fix review findings: stale abort() docs + move RFC to implemented

Codex's no-ship was a completeness/docs-sync gap, not loop behavior:

- docs/architecture.md: drop the public abort() handle row; the teardown
  signal is now cancel() then await whenIdle().
- cancel.spec.ts: the module doc and the turn-start comment contrasted
  cancel() against a public abort() verb that no longer exists — reword to
  name the loop's private step AbortController.
- packages/ui/acp/src/index.ts: the post-resume-leak comment cited abort();
  cancel() is the surviving stop verb that likewise does not unregister.
- Move the RFC proposed -> implemented/simplification with amended text:
  Status flips, the both-removal proposal is narrowed to abort-only, and an
  implementation note records why whenIdle() is retained (load-bearing
  quiescence primitive with live ACP consumers). Update docs/rfc/README.md.
- AGENTS.md "RFCs are proposals, not golden truth": add the concrete
  abort/whenIdle worked example now that the implemented RFC exists to link.
- Regenerate the cordis catalog (line-number drift from the rebase).

docs/rfc/README.md

@@ -51,7 +51,6 @@ Do NOT write one for a mechanical or local choice (a variable name, a one-file r
 |---|---|
 | [Unify the agent id and the session id](proposed/simplification/2026-06-20-unify-agent-and-session-id.md) | 2026-06-20 |
 | [Stop mirroring durable boundaries as agent events](proposed/simplification/2026-06-20-remove-agent-boundary-mirror-events.md) | 2026-06-20 |
-| [Keep one public stop primitive](proposed/simplification/2026-06-20-public-agent-stop-surface.md) | 2026-06-20 |
 | [Fold trace-only session facts into load-bearing events](proposed/simplification/2026-06-20-collapse-trace-only-session-events.md) | 2026-06-20 |
 
 ### Architecture
@@ -95,6 +94,7 @@ Do NOT write one for a mechanical or local choice (a variable name, a one-file r
 | [Drop unconsumed assembled LLM convenience surfaces](implemented/simplification/2026-06-20-drop-unconsumed-llm-assembled-surfaces.md) | 2026-06-20 |
 | [Drop the unconsumed `llm/adapter-change` event](implemented/simplification/2026-06-20-drop-unconsumed-llm-adapter-change-event.md) | 2026-06-20 |
 | [Prune dead methods from the persistence and bash seams](implemented/simplification/2026-06-20-prune-dead-seam-methods.md) | 2026-06-20 |
+| [Keep one public stop primitive](implemented/simplification/2026-06-20-public-agent-stop-surface.md) | 2026-06-20 |
 
 ### Architecture