agent: OverflowMenu — trimmed to rebuild + dashboard link

Deliberately trimmed vs. app.js's `populateOverflowMenu`, which held
dashboard-link/rebuild/new-session/logout/model-picker/effort-picker
all in one flat list — the design guide's own named junk-drawer
anti-example. Model/effort already moved to StatusChips' own
Badge+Dropdown controls; new-session/logout now live as TermInput
slash commands (typed, with their own two-step confirm). What's left —
rebuild + a dashboard back-link — is genuinely menu-shaped (rare, not
tied to any other visible control), so it's still a `⋯` menu, just a
much shorter one.

Reuses `@hive/shared`'s Badge+Dropdown pair (same anchored-popover
shape as StatusChips' model/effort pickers), not a bespoke popover.
Rebuild's confirm is the same "select once to arm, select again to
fire" idea as the slash commands, adapted to a menu click. New
`lib/rebuildAction.ts` — same cross-origin-needs-a-real-form-submit
reasoning as pauseAction.ts (hive-c0re's `/api/rebuild/{name}` has no
CORS header either).

Found + fixed a real layout gap in the shared Dropdown while
screenshot-verifying: its CSS anchors left-edge-to-left-edge, correct
for a picker with room to its right, but the overflow trigger is the
header's right-most element, so the menu ran off-screen. Fixed with a
scoped override in this component's own CSS (`.header-overflow-anchor
.ui-dropdown { left: auto; right: 0; }`) rather than changing the
shared default, which is still correct for every other caller.

frontend/packages/agent/src/Root.tsx

@@ -12,6 +12,7 @@ import { SidePanel } from './components/SidePanel.js';
 import { InboxPanel } from './components/InboxPanel.js';
 import { TodosPanel } from './components/TodosPanel.js';
 import { TermInput } from './components/TermInput.js';
+import { OverflowMenu } from './components/OverflowMenu.js';
 import { useAgentState } from './hooks/useAgentState.js';
 import { useTodos } from './hooks/useTodos.js';
 import { fmtAge, fmtTokens } from './lib/format.js';
@@ -68,6 +69,10 @@ export function Root() {
     <>
       <HeaderPill kind="inbox" icon="📬" label="inbox" count={state?.inbox.length ?? 0} onClick={() => setOpenPanel('inbox')} />
       <HeaderPill kind="todos" icon="📋" label="todos" count={todos.length} onClick={() => setOpenPanel('todos')} />
+      {/* Needs dashboard_port from a loaded snapshot — omitted (like the
+       * old page's populateOverflowMenu) until the first /api/state
+       * resolves. */}
+      {state ? <OverflowMenu label={state.label} dashboardBase={resolveDashboardBase(state.dashboard_port)} /> : null}
     </>
   );
   // Kept mounted regardless of `openPanel` (open/closed toggles just the

frontend/packages/agent/src/components/OverflowMenu.css

@@ -0,0 +1,19 @@
+/* Anchors <Dropdown> under the "⋯" trigger — same positioning
+   contract as StatusChips.css's `.status-chip-anchor`, kept as its own
+   rule here rather than reused across components (see this file's
+   sibling .tsx comment) so OverflowMenu doesn't depend on StatusChips'
+   incidental CSS. */
+.header-overflow-anchor {
+  position: relative;
+  display: inline-block;
+}
+/* @hive/shared's Dropdown.css anchors left-edge-to-left-edge, correct
+   for a picker with room to its right (StatusChips' model/effort). The
+   overflow trigger is the header's right-most element instead, so a
+   left anchor pushes the menu off-screen — flip to right-edge-to-
+   right-edge here, scoped to this one consumer rather than changing
+   the shared default (which is still correct for every other caller). */
+.header-overflow-anchor .ui-dropdown {
+  left: auto;
+  right: 0;
+}

frontend/packages/agent/src/components/OverflowMenu.tsx

@@ -0,0 +1,66 @@
+// <OverflowMenu> — the header's `⋯` trigger. Deliberately trimmed vs.
+// app.js's `populateOverflowMenu`: that one held dashboard-link/rebuild/
+// new-session/logout/model-picker/effort-picker all in one flat list —
+// the design guide's own named anti-example for a junk drawer. The
+// model/effort pickers already moved to StatusChips' own Badge+Dropdown
+// controls (this rewrite's first commit); new-session/logout now live
+// as TermInput slash commands (typed, not menu-clicked, and already
+// have their own two-step confirm). What's left here — rebuild + a
+// dashboard back-link — are genuinely menu-shaped (rare, not tied to
+// any other visible control), so they're still a `⋯` menu, just a much
+// shorter one.
+//
+// Reuses `@hive/shared`'s `Badge`+`Dropdown` — same anchored-popover
+// pair StatusChips' model/effort pickers use, not a bespoke popover.
+// Rebuild's confirm is the same "select once to arm, select again to
+// fire" pattern as TermInput's `/new-session`/`/logout` — adapted here
+// to a menu click instead of a typed repeat, but the same "requires
+// deliberate repetition, not a modal" idea.
+import { useState } from 'preact/hooks';
+import { Badge } from '@hive/shared/badge.js';
+import { Dropdown, type DropdownOption } from '@hive/shared/dropdown.js';
+import { submitRebuild } from '../lib/rebuildAction.js';
+import './OverflowMenu.css';
+
+export interface OverflowMenuProps {
+  label: string;
+  dashboardBase: string;
+}
+
+export function OverflowMenu({ label, dashboardBase }: OverflowMenuProps) {
+  const [open, setOpen] = useState(false);
+  const [armed, setArmed] = useState(false);
+
+  function close() {
+    setOpen(false);
+    setArmed(false);
+  }
+
+  const options: DropdownOption[] = [
+    { value: 'dashboard', label: '↑ dashboard' },
+    { value: 'rebuild', label: armed ? '↻ rebuild — click again to confirm' : '↻ rebuild container' },
+  ];
+
+  function onSelect(value: string) {
+    if (value === 'dashboard') {
+      window.open(`${dashboardBase}dashboard.html`, '_blank', 'noopener');
+      close();
+      return;
+    }
+    if (value === 'rebuild') {
+      if (armed) {
+        submitRebuild(dashboardBase, label);
+        close();
+      } else {
+        setArmed(true);
+      }
+    }
+  }
+
+  return (
+    <div class="header-overflow-anchor">
+      <Badge value="⋯" title="more actions" onClick={() => setOpen((o) => !o)} expanded={open} />
+      <Dropdown open={open} options={options} label="more actions" onSelect={onSelect} onClose={close} />
+    </div>
+  );
+}

frontend/packages/agent/src/lib/rebuildAction.ts

@@ -0,0 +1,11 @@
+// Rebuild POST to the *dashboard's* origin — same cross-origin-needs-a-
+// real-form-submit reasoning as pauseAction.ts's `submitPauseResume`
+// (hive-c0re's `/api/rebuild/{name}` returns a plain 200, no CORS
+// header, so a cross-origin `fetch` can't read the result).
+export function submitRebuild(dashboardBase: string, label: string): void {
+  const form = document.createElement('form');
+  form.method = 'POST';
+  form.action = `${dashboardBase}api/rebuild/${label}`;
+  document.body.appendChild(form);
+  form.submit();
+}