docs: retire the agent hierarchy from every page that described it

The topology doc keeps its filename and its second half (manager
special-casing, harness unit shape) — both are cross-referenced from
other pages and neither is about the parent field. Its first half is
rewritten: what topology.json is now, and a table of what the removal
took with it, so a reader who finds `<parent>` or `set-parent` in an old
issue thread learns it went away rather than moved.

The dashboard's tree-rendering section is marked dormant rather than
deleted: the walk is still in swarm.js and retiring it is the frontend
owner's call.

docs/web-ui/dashboard.md

@@ -56,16 +56,12 @@ surfaces, not tab panes.
 
 ## SW4RM tab
 
-**C0NTAINERS** — live containers rendered as a depth-first
-tree using `ContainerView.parent` (populated by
-`hive-c0re/src/agent_config/topology.rs` — don't confuse it with
-`hive-c0re/src/dashboard/topology.rs`, which only holds the
-set-parent endpoints).
-ASCII tree glyphs (`├─`, `└─`, `│  ` continuation columns) prefix
-each container's row, showing the agent parent/child hierarchy.
-When every container has `parent = null`
-(flat topology) the tree collapses to a plain list with no
-glyphs. The tree sorts children alphabetically within each parent;
+**C0NTAINERS** — live containers rendered as a flat,
+alphabetically-sorted list. The renderer still walks
+`ContainerView.parent` for a depth-first tree with ASCII glyphs
+(`├─`, `└─`, `│  ` continuation columns), but #4472 removed that field,
+so every row sits at depth 0 and the renderer paints no glyph. The tree
+sorts alphabetically;
 roots likewise. The tree tolerates cycles in the parent graph —
 it appends orphaned containers (not reachable from any root)
 as roots so no agent disappears. Pulsing red banner at the top
@@ -961,7 +957,7 @@ Three primitives, all built on the `openDialog` core:
   summaries are sticky (select to dismiss) so they aren't missed.
 
 Every destructive run-state action (`ST0P`, `R3ST4RT`, `R3BU1LD`,
-`DESTR0Y`, `PURG3`, `M0V3`) routes through `themedConfirm`, on both
+`DESTR0Y`, `PURG3`) routes through `themedConfirm`, on both
 the per-agent `⋮` menu and the bulk selection bar.
 
 **Graceful stop** — the `■ ST0P` confirm dialog (per-agent and
@@ -985,10 +981,12 @@ identically.)
 
 ### Topology tree
 
-See **SW4RM tab** above for the parent/child derivation, sibling
-sort order, and cycle-safety rules (`swarm.js::buildAgentTree` walks
-`ContainerView.parent`) — this section covers only how the tree is
-*drawn*.
+⚠️ **Dormant since #4472,** which removed `ContainerView.parent`:
+`buildAgentTree` now puts every container at depth 0 and the rules below are
+all no-ops — the list renders flat. The walk and the prefix painting are
+still in `swarm.js`; retiring them falls to the frontend owner rather
+than to this removal. What follows describes what the code
+still does, for whoever makes that call.
 
 The per-row prefix column (`.tree-prefix`) is **DOM-painted, not
 text-glyph-painted**: each indent lane is its own positioned `<span>`
@@ -1002,8 +1000,8 @@ ancestor's still-open subtree, and the joint at a row's own depth is
 the row's icon midline). Exact lane widths and positioning live in
 `swarm.js`'s tree-prefix rendering and its paired CSS rules — not
 reproduced here since they're tuned in pixel units and will drift.
-When every container is at depth 0 (no `parent` set) these rules are
-all no-ops and the layout reads like a plain flat list.
+With every container at depth 0 these rules are all no-ops and the
+layout reads like a plain flat list, which is what a hive renders today.
 
 ## Selection bar
 
@@ -1032,25 +1030,10 @@ frosted-mauve bar slides up from the bottom of the viewport
   - `▶ R3SUM3` — paused agents only
   - `↻ R3BU1LD` — always available
   - `DESTR0Y` / `PURG3` — always available
-  - `⇡ M0V3 → ROOT` — promote selected agents to top-level
-    (parent = null); disabled when all selected are already at root.
-    hive-c0re's `topology::set_parent` refuses moves it can't satisfy
-    (for example a move that would create a cycle) and the refusal surfaces
-    in the failure roll-up.
-  - `⇢ M0V3 → [select]` — 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
-    hive-c0re re-checks per-agent). On submit:
-    - **single agent** → `POST /api/topology/set-parent`
-      (form-encoded `child=<name>&new_parent=<target>`)
-    - **multiple agents** → `POST /api/topology/set-parent-bulk`
-      (JSON `[{ child, new_parent }]`; all moves land in a single
-      `topology.json` commit instead of one per agent)
 <!-- vale write-good.Passive = YES -->
 
-    Both write `topology.json` and re-emit a container snapshot so
-    the tree repaints without a page reload.
+  #4472 removed the `M0V3` picker that used to sit here — an agent has
+  no parent to move it to any more.
 - **`✕ clear`** button + `Esc` key clear the entire selection.
 
 Every render prunes stale selections (agents destroyed while