fix review findings: whenIdle() is observation, not the teardown await

Codex's confirmation pass found the teardown-framing error went deeper than the
three prose spots already fixed: the whenIdle() JSDoc itself (and its mirrors)
claimed "the quiescence signal a teardown awaits ... a lifecycle owner disposes
the agent through its AgentHandle which ... awaits THIS". The disposer does not
call whenIdle() — it does `stop(); await agent.done` directly
(packages/core/agent-loop/src/index.ts:271). whenIdle() is the NON-OWNER
observation hook; owner teardown awaits the loop-exit promise (done) through
AgentHandle.dispose(). Reframe every copy accordingly:

- packages/core/agent/src/types.ts: the Agent.whenIdle() contract JSDoc.
- packages/core/agent-loop/src/agent.ts: the impl JSDoc.
- packages/core/agent/README.md and docs/core-data-structures/core.md (the
  type-equiv mirror of the types.ts JSDoc — re-copied verbatim).
- docs/rfc/proposed/feature/2026-06-14-acp-agent-client-protocol.md:40 and :70:
  owner teardown via AgentHandle.dispose(); a non-owner observing quiescence
  uses the interface-level agent.whenIdle(), not hand-rolled agent/status.
- Regenerate the cordis catalog (whenIdle source line moved).

packages/core/agent-loop/src/agent.ts

@@ -228,8 +228,10 @@ export class ReactLoopAgent implements Agent {
    * internal waiter (see {@link idleWaiters}) released on the next
    * running→idle/disposed transition, resolving on `idle` directly (the turn
    * fully ended) or chaining {@link done} on `disposed` (wait for the loop to
-   * actually exit). Implements the {@link Agent.whenIdle} contract used by
-   * teardown (handle disposal aborts in-flight work, then awaits `whenIdle()`).
+   * actually exit). Implements the {@link Agent.whenIdle} contract: a non-owner
+   * quiescence-observation hook, distinct from teardown (a lifecycle owner stops
+   * and unregisters via `AgentHandle.dispose()`, which awaits {@link done}
+   * directly, not through this).
    */
   whenIdle(): Promise<void> {
     if (this._status === 'disposed') return this.done

packages/core/agent/README.md

@@ -57,7 +57,7 @@ The handle every plugin programs against:
 - `agent.steer(content, options?)` — steer a running turn (inject between steps); behaves like `send` when idle
 - `agent.inject(content, options?)` — inject in-session context (context/message event); the next request sees it. Does not run the model. While a turn is open it joins that turn; while idle it is wrapped in a one-shot `injection` turn so every event stays turn-enclosed ([the turn-enclosure invariant](../../../docs/rfc/implemented/architecture/2026-06-15-turn-enclosure-invariant.md))
 - `agent.cancel(reason?)` — cancel ALL pending work: clears the queued + steering FIFOs, aborts the in-flight step, and drops a turn about to start (the pre-step window) so a queued-but-not-started prompt never runs. A UI/ACP `session/cancel` maps to this. The single public stop primitive. Idle with nothing pending → a safe no-op.
-- `agent.whenIdle()` — resolve once the agent reaches quiescence after settling out of `running` (idle → immediately; disposed → awaits the loop exit), the signal a teardown awaits (a lifecycle owner disposes the handle, which aborts in-flight work then awaits this). Observes the transition without disposing the agent.
+- `agent.whenIdle()` — resolve once the agent reaches quiescence after settling out of `running` (idle → immediately; disposed → awaits the loop exit). A non-owner's quiescence-observation hook: it observes the work settling WITHOUT tearing the agent down. Teardown is separate — a lifecycle owner stops and unregisters via `AgentHandle.dispose()`, which awaits the loop exit directly.
 - `agent.session`, `agent.status`, `agent.options`, `agent.id`
 
 ### Extension points

packages/core/agent/src/types.ts

@@ -99,12 +99,14 @@ export interface Agent {
 
   /**
    * Resolve once the agent has reached quiescence after settling out of
-   * `running`, or immediately if it is already idle with no queued work. The
-   * quiescence signal a teardown awaits: a lifecycle owner disposes the agent
-   * through its `AgentHandle` (which aborts in-flight work then awaits this), so
-   * the caller proceeds only after queued/running work has fully stopped (a
-   * closing ACP connection, a disposing UI plugin) rather than returning while
-   * the driver is still streaming or about to start a queued turn.
+   * `running`, or immediately if it is already idle with no queued work. A
+   * non-owner's quiescence-observation hook: a consumer that does NOT own the
+   * agent's lifecycle (a closing ACP connection, a UI plugin) awaits this to
+   * proceed only after queued/running work has fully stopped, rather than
+   * returning while the driver is still streaming or about to start a queued
+   * turn. It does NOT tear the agent down — a lifecycle owner stops and
+   * unregisters the agent through its `AgentHandle.dispose()` (which awaits the
+   * loop-exit promise directly), separate from this.
    *
    * "Quiescence", not merely "status changed": a disposed agent emits
    * `agent/status('disposed')` from inside its disposer, BEFORE the driver loop
@@ -112,10 +114,6 @@ export interface Agent {
    * to actually exit (the implementation chains the loop-exit promise), not just
    * observe the status flip. A mid-step disposal that never reaches `idle` still
    * unblocks the await this way.
-   *
-   * Distinct from disposal: `whenIdle()` observes the transition WITHOUT tearing
-   * the agent down. A consumer that owns the agent's lifecycle disposes it
-   * separately.
    */
   whenIdle(): Promise<void>