dashboard #486: drop manager special-case + enable M0V3 picker for multi-select (mara on #695)

Two changes from mara's review:

1. drop the manager special-case. Both M0V3 affordances now apply
   regardless of whether the manager is in the selection; backend
   topology::set_parent refuses the manager move and the failure
   surfaces in the bulk-action error roll-up. Matches the #443 ST0P
   policy of 'don't pre-gate manager actions, let the backend speak'.

2. enable the M0V3 → <pick> picker for multi-select. Was single-agent
   only in v1. Picker now omits every selected agent itself plus the
   union of every selected agent's descendants (cycle-safe across the
   whole batch); on submit POSTs once per selected agent sequentially,
   same shape as the existing bulk-button loop. Confirm message +
   error roll-up adapt to selection size.

docs/web-ui.md updated to match.

docs/web-ui.md

@@ -440,6 +440,19 @@ frosted-mauve bar slides up from the bottom of the viewport
   - `▶ ST4RT` — stopped agents only
   - `↻ R3BU1LD` — always available
   - `DESTR0Y` / `PURG3` — sub-agents only (disabled if manager selected)
+  - `⇡ M0V3 → ROOT` (#486) — promote selected agents to top-level
+    (parent = null); disabled when all selected are already at root.
+    Manager included with no special-case (matches the `ST0P` policy);
+    the backend's `topology::set_parent` refuses to move the manager
+    and the refusal surfaces in the failure roll-up.
+  - `⇢ M0V3 → [select]` (#486) — inline picker available for any
+    selection size. The dropdown lists every container that isn't IN
+    the selection itself nor a descendant of any selected agent
+    (client-side BFS cycle prevention across the whole batch; the
+    backend re-checks per-agent). On submit POSTs to
+    `/api/topology/set-parent` (form-encoded `child=<name>&new_parent=<target>`)
+    once per selected agent, which writes `topology.json` and re-emits
+    a container snapshot so the tree repaints without a page reload.
 - **`✕ clear`** button + `Esc` key clear the entire selection.
 
 Stale selections (agents destroyed while selected) are pruned on

frontend/packages/dashboard/src/dashboard.css

@@ -915,6 +915,11 @@ ul form.inline { display: inline-block; }
 .btn-restart { color: var(--cyan); border-color: var(--cyan); font-size: 0.75em; padding: 0.15em 0.5em; margin-left: 0.6em; }
 .btn-stop    { color: var(--pink); border-color: var(--pink); font-size: 0.75em; padding: 0.15em 0.5em; margin-left: 0.6em; }
 .btn-start   { color: var(--green); border-color: var(--green); font-size: 0.75em; padding: 0.15em 0.5em; margin-left: 0.6em; }
+/* #486 — M0V3 affordance (selection bar). Mauve picks up the same
+   accent the question-override / mid-status surfaces use; reads as
+   "structural change" rather than the destructive red / amber chrome
+   of destroy / rebuild. */
+.btn-move    { color: var(--mauve); border-color: var(--mauve); font-size: 0.75em; padding: 0.15em 0.5em; margin-left: 0.6em; }
 .btn-talk { color: var(--cyan); border-color: var(--cyan); }
 .btn-spawn { color: var(--amber); border-color: var(--amber); }
 .btn-fire-now { color: var(--mauve, #cba6f7); border-color: var(--mauve, #cba6f7); }
@@ -2085,3 +2090,32 @@ body.flow-shell .tabbar .tab.active.tab-link {
    visible (`body.has-selection`, toggled by tabs.js when the
    selection set is non-empty). */
 body.dashboard-shell.has-selection { padding-bottom: 4.5em; }
+
+/* #486 — M0V3 → <pick> picker. Inline `<select>` + button pair
+   sitting alongside the bulk action buttons in the selection bar.
+   The select inherits the terminal-y monospace look so it doesn't
+   read as system-chrome popping out of the swarm aesthetic. Only
+   surfaces when exactly one agent is selected. */
+.move-picker {
+  display: inline-flex;
+  align-items: center;
+  gap: 0.3em;
+  margin-left: 0.6em;
+}
+.move-picker-select {
+  font-family: inherit;
+  font-size: 0.75em;
+  background: var(--bg);
+  color: var(--fg);
+  border: 1px solid var(--mauve);
+  border-radius: 2px;
+  padding: 0.1em 0.3em;
+  max-width: 16em;
+}
+.move-picker-select:disabled {
+  opacity: 0.5;
+  cursor: default;
+}
+.move-picker .btn-move {
+  margin-left: 0;
+}

frontend/packages/dashboard/src/tabs.js

@@ -864,6 +864,146 @@ window.marked = marked;
       confirm: (names) => `PURGE ${names.length} agent${names.length === 1 ? '' : 's'} (${names.join(', ')})? containers, config history, claude creds, and notes are all WIPED. no undo.`,
       disabledTitle: why('PURG3', managerNames.map((n) => `\`${n}\` is the manager`)),
     });
+
+    // #486 — move agent(s) in the topology tree. Two affordances:
+    //
+    //   ⇡ M0V3 → ROOT   promote selected agent(s) to top-level (parent=null)
+    //   ⇢ M0V3 → [sel]  reparent the single selected agent under a picked
+    //                   parent (cycle-safe — the dropdown filters out self
+    //                   and own descendants on the client side; the
+    //                   backend rechecks via `topology::set_parent`).
+    //
+    // Backend lives at POST /api/topology/set-parent (dashboard.rs#2170),
+    // form-encoded `child=<name>&new_parent=<target-or-empty>`. The
+    // backend re-emits container snapshots on success, so the tree
+    // repaints without a separate refresh.
+    addMoveActions(actions, selected, containers);
+  }
+
+  // #486 — render the M0V3 affordances inside the selection bar. Split
+  // into its own helper because the picker variant needs a select + button
+  // pair, not the single-button shape addBulkButton ships.
+  //
+  // No client-side manager special-case (mara on #695): backend
+  // `topology::set_parent` refuses to move the manager and surfaces the
+  // refusal as a per-agent failure in the bulk-action error roll-up. Same
+  // pattern as #443 ST0P (which also doesn't special-case manager).
+  function addMoveActions(parent, selected, containers) {
+    // M0V3 → ROOT: parent=null for every selected agent. Only meaningful
+    // when at least one selected agent currently has a non-null parent;
+    // otherwise it's a no-op for everything.
+    const someNotAtRoot = selected.some((c) => c.parent);
+    addBulkButton(parent, 'btn-move', '⇡ M0V3 → ROOT', someNotAtRoot, selected, {
+      action: '/api/topology/set-parent',
+      perAgentBodyFor: (name) => ({ child: name, new_parent: '' }),
+      confirm: (names) => `promote ${names.length} agent${names.length === 1 ? '' : 's'} (${names.join(', ')}) to top-level (parent → root)?`,
+      disabledTitle: !someNotAtRoot
+        ? '⇡ M0V3 → ROOT not available — all selected agents are already at root'
+        : null,
+    });
+
+    // M0V3 → <pick>: inline `<select>` of candidate parents + submit
+    // button. Available for any selection size (mara on #695 — was
+    // single-agent only in v1). Picker omits each selected agent itself
+    // plus the union of every selected agent's descendants (cycle-safe;
+    // backend `topology::set_parent` re-checks). Empty candidate list ⇒
+    // disable the picker.
+    const candidates = validReparentCandidates(selected, containers);
+    const wrap = el('span', { class: 'move-picker' });
+    const selectTitle = selected.length === 1
+      ? `change ${selected[0].name}'s parent`
+      : `change ${selected.length} agents' parent`;
+    const sel = el('select', { class: 'move-picker-select', title: selectTitle });
+    sel.append(el('option', { value: '' }, '— pick parent —'));
+    for (const name of candidates) {
+      sel.append(el('option', { value: name }, name));
+    }
+    if (!candidates.length) {
+      sel.disabled = true;
+      sel.title = selected.length === 1
+        ? `no valid parents for ${selected[0].name} (every other agent is its descendant)`
+        : `no valid parents — every other agent is a descendant of one of the selected`;
+    }
+    const btn = el('button', { type: 'button', class: 'btn btn-move' }, '⇢ M0V3');
+    btn.disabled = true;
+    sel.addEventListener('change', () => { btn.disabled = !sel.value; });
+    btn.addEventListener('click', async () => {
+      const newParent = sel.value;
+      if (!newParent) return;
+      const names = selected.map((c) => c.name);
+      const promptMsg = names.length === 1
+        ? `move ${names[0]} under ${newParent}?`
+        : `move ${names.length} agents (${names.join(', ')}) under ${newParent}?`;
+      if (!confirm(promptMsg)) return;
+      btn.disabled = true;
+      const original = btn.innerHTML;
+      btn.innerHTML = '<span class="spinner">◐</span> ⇢ M0V3';
+      // Sequential POSTs — same shape as the bulk-button loop. Each
+      // call is small + backend serialises topology writes via the
+      // file-lock anyway.
+      const failures = [];
+      for (const name of names) {
+        try {
+          const body = new URLSearchParams({ child: name, new_parent: newParent });
+          const resp = await fetch('/api/topology/set-parent', {
+            method: 'POST',
+            headers: { 'Content-Type': 'application/x-www-form-urlencoded' },
+            body,
+            redirect: 'manual',
+          });
+          const ok = resp.ok || resp.type === 'opaqueredirect'
+            || (resp.status >= 200 && resp.status < 400);
+          if (!ok) {
+            const text = await resp.text().catch(() => '');
+            failures.push(`${name}: http ${resp.status}${text ? ' — ' + text.slice(0, 200) : ''}`);
+          }
+        } catch (err) {
+          failures.push(`${name}: ${err}`);
+        }
+      }
+      btn.innerHTML = original;
+      btn.disabled = !sel.value;
+      if (failures.length) {
+        alert(`⇢ M0V3 completed with ${failures.length} failure${failures.length === 1 ? '' : 's'}:\n\n` + failures.join('\n'));
+      }
+    });
+    wrap.append(sel, btn);
+    parent.append(wrap);
+  }
+
+  // Filter the dashboard's container list to those that are valid
+  // re-parent targets for the `selected` agents: anyone who isn't IN
+  // the selection itself, isn't a descendant of any selected agent
+  // (cycle prevention across the whole batch). The backend re-checks
+  // per-agent via `topology::set_parent`; this client-side filter is
+  // purely UX so the operator can't pick an obviously-invalid option.
+  function validReparentCandidates(selected, containers) {
+    // Build child map once.
+    const childrenOf = new Map();
+    for (const c of containers) {
+      const p = c.parent || null;
+      if (!childrenOf.has(p)) childrenOf.set(p, []);
+      childrenOf.get(p).push(c.name);
+    }
+    // Union descendant set across every selected agent (each agent's
+    // descendants AND itself).
+    const blocked = new Set();
+    for (const t of selected) {
+      const queue = [t.name];
+      blocked.add(t.name);
+      while (queue.length) {
+        const n = queue.shift();
+        for (const child of (childrenOf.get(n) || [])) {
+          if (blocked.has(child)) continue;
+          blocked.add(child);
+          queue.push(child);
+        }
+      }
+    }
+    return containers
+      .filter((c) => !blocked.has(c.name))
+      .map((c) => c.name)
+      .sort();
   }
 
   function addBulkButton(parent, btnClass, label, enabled, selected, opts) {
@@ -887,10 +1027,25 @@ window.marked = marked;
       // Sequential POSTs to keep server-side serialisation predictable
       // (rebuild_queue dedups but other endpoints don't); the loop is
       // short — bulk selections are typically a handful of agents.
+      //
+      // Two URL shapes:
+      //  - `opts.action` is a path prefix and the agent name gets
+      //    appended (lifecycle endpoints: /start/<name>, /rebuild/<name>).
+      //    `opts.body` is a static object applied to every POST.
+      //  - `opts.perAgentBodyFor(name)` is set: `opts.action` is the
+      //    full URL (no name appended) and the per-agent body comes
+      //    from the callback. Used by /api/topology/set-parent (#486),
+      //    where the agent name is a body field rather than a URL
+      //    component.
       for (const name of names) {
-        const body = new URLSearchParams(opts.body || {});
+        const body = opts.perAgentBodyFor
+          ? new URLSearchParams(opts.perAgentBodyFor(name))
+          : new URLSearchParams(opts.body || {});
+        const url = opts.perAgentBodyFor
+          ? opts.action
+          : opts.action + encodeURIComponent(name);
         try {
-          const resp = await fetch(opts.action + encodeURIComponent(name), {
+          const resp = await fetch(url, {
             method: 'POST',
             headers: { 'Content-Type': 'application/x-www-form-urlencoded' },
             body,

nix/templates/harness-base.nix

@@ -1269,8 +1269,17 @@ in
         # `hyperhive.user.passwordlessSudo = true` is configured
         # (#672 fixup pulled forward into this PR to avoid the
         # regression argus flagged on #676).
+        #
+        # `systemd.services.<name>.path` appends `/bin` to each entry,
+        # so the bare prefixes here resolve to `/run/wrappers/bin` +
+        # `/run/current-system/sw/bin` inside the unit's PATH. Passing
+        # the trailing `/bin` ourselves (the natural-looking spelling)
+        # would yield `/run/wrappers/bin/bin` + `/run/current-system/sw/bin/bin`,
+        # neither of which exists — that's how #672 originally landed
+        # broken: every agent had a PATH pointing at non-existent dirs
+        # and `which sudo` kept falling back to the un-setuid binary.
         path = [
-          "/run/wrappers/bin"
+          "/run/wrappers"
           "/run/current-system/sw"
         ];
         environment = {