docs: document rebuild queue panel + module (follow-up to #340)

docs/web-ui.md

@@ -122,7 +122,21 @@ the previous process's socket release resolves itself.
    meta-update running" banner and the update button is disabled
    (snapshot field `meta_update_running`, live event
    `meta_update_running`).
-5. **M1ND H4S QU3STI0NS** — pending operator-targeted `ask`
+5. **R3BU1LD QU3U3** — pending and recently-completed container
+   operations: rebuilds, meta-update cascades, and first-spawns.
+   One operation runs at a time; the worker drains FIFO. Each row
+   shows a state glyph (`⏸` queued / `▶` running / `✔` done /
+   `✖` failed / `⊘` cancelled), kind glyph + verb (`↻ rebuild`,
+   `◆ meta_update`, `✨ spawn`, `🗑 destroy`), agent name, source
+   chip (`manual | meta_update | auto_update | crash_recover`),
+   timing, and an optional reason / error. Meta-update cascade
+   rebuilds nest under their parent entry (`parent_id` grouping;
+   `rqe-child` CSS class). Dedup: re-enqueueing a still-queued op
+   for the same agent collapses into the existing entry. Running
+   entries tick elapsed seconds live (same pattern as the TTL
+   countdown). Cold-loaded from `/api/state.rebuild_queue`; live
+   updates via `rebuild_queue_changed` snapshot event.
+6. **M1ND H4S QU3STI0NS** — pending operator-targeted `ask`
    questions, i.e. rows with `target IS NULL` (peer-to-peer
    questions live in the same table but never surface here)
    (amber pulsing border). Free-text fallback always rendered
@@ -132,23 +146,23 @@ the previous process's socket release resolves itself.
    with `[cancelled]`. Questions with a `ttl_seconds` show a
    `⏳ MM:SS` chip; the host-side watchdog auto-cancels with
    `[expired]` when the deadline fires.
-6. **QU3U3D R3M1ND3RS** — reminders agents have scheduled for
+7. **QU3U3D R3M1ND3RS** — reminders agents have scheduled for
    themselves (via the `remind` tool) but not yet delivered.
    Each row shows the owner, due time, and message; a `CANC3L`
    button hard-deletes (`POST /cancel-reminder/{id}`) and a
    `R3TRY` button re-arms one whose delivery failed
    (`POST /retry-reminder/{id}`). Backed by `GET /api/reminders`.
-7. **P3NDING APPR0VALS** — the queue (see "Approval card"
+8. **P3NDING APPR0VALS** — the queue (see "Approval card"
    below). The R3QU3ST SP4WN form lives at the top of this
    section since submitting it immediately queues an approval
    that lands directly below.
-8. **0PER4T0R 1NB0X** — recent messages addressed to `operator`,
+9. **0PER4T0R 1NB0X** — recent messages addressed to `operator`,
    derived client-side from the dashboard event stream (no longer
    a snapshot field). Cold load seeds from
    `/dashboard/history`'s 200-message backfill; subsequent
    `sent` events with `to == "operator"` are appended live. Cap
    50, newest-first.
-9. **MESS4GE FL0W** — live broker tail wrapped in a
+10. **MESS4GE FL0W** — live broker tail wrapped in a
    `.terminal-wrap` (same chrome as the per-agent terminal).
    Cold load backfills the last ~200 messages from
    `/dashboard/history`; live frames arrive on
@@ -388,6 +402,13 @@ payload):
   `crash_watch` poll. Client upserts/removes by name; the
   pending overlay is read from `transientsState` since the
   payload doesn't carry it.
+- `rebuild_queue_changed` (seq, queue: `Vec<QueueEntry>`) —
+  full snapshot of the rebuild queue on every mutation (enqueue,
+  state transition, dedup collapse, terminal-history trim).
+  Same snapshot-over-diff rationale as `tombstones_changed` /
+  `meta_inputs_changed`: the list is small and the client's
+  `parent_id` grouping is most naturally re-derived from the
+  full list. Cold-loaded from `/api/state.rebuild_queue`.
 
 `/api/state` is **only fetched on cold-load and on the few
 forms that mutate non-event-derived state** (PURG3 +