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).

packages/core/agent-loop/tests/cancel.spec.ts

@@ -1,7 +1,8 @@
 /**
  * Tests for the queue-aware `Agent.cancel()` primitive. `cancel()` is the
  * broad verb — it clears queued + steering work, aborts an in-flight step, and
- * drops a turn about to start — whereas `abort()` kills only the current step.
+ * drops a turn about to start — whereas a bare step abort (the loop's private
+ * `AbortController`) kills only the current step and leaves the queue intact.
  * These tests exercise every window where a cancel can land (idle, pre-step,
  * mid-step, continuation) and the marker's arm/reset rules that keep a cancel
  * from leaking to a later prompt or hanging `whenIdle()`.
@@ -172,7 +173,7 @@ describe('Agent.cancel()', () => {
 
     // A turn-start listener fires BEFORE any AbortController is installed for the
     // step. Cancelling there must still drop the step (the turn-scoped marker,
-    // not abort(), is what catches this) — no model step runs.
+    // not the step AbortController, is what catches this) — no model step runs.
     let streamed = false
     ctx.on('agent/stream-chunk', () => { streamed = true })
     const dispose = ctx.on('agent/turn-start', (subject) => {