fix(acp): settle admission-blocked and retried prompts after the merge

The automation bridge inherited two master-era assumptions the message
machine no longer honors. A prompt blocked at pre-turn admission opens no
turn, so no turn/end could ever settle it — the bridge now watches
whenIdle() and reports a turnless slot as cancelled (the disposed-agent
guard moved to a registry identity check before send). A failed turn no
longer rejects at its turn/end either: agent.retry() closes the failed
turn and opens a successor on the same history, so the bridge holds the
terminal error and lets a retry-triggered turn/start adopt the prompt,
rejecting only at quiescence with no successor.

Also: refresh the empty-response-retry fixture for retry-as-turn logging,
adapt master-side tests to the unified send()/UserMessageData API and
registry-fact disposal, resync the doc pairs both sides touched, trim
architecture.md back under its word ceiling, and regenerate the event and
persistence catalogs.

docs/core-data-structures/session.i18n.yaml

@@ -2,5 +2,5 @@
 # side as of the last confirmed-consistent state. Both languages carry equal authority;
 # after editing either side, bring the other along and re-record with:
 #   pnpm run verify-translation-pairing --write
-session.md: d789ffcabb5cb0c744e265b61e322831c1d8a04f
-session.zh.md: f4f102861db7403520e9f38cb56613e430718cbe
+session.md: 201f366388b7a122ea0b59ce95b20b379f771796
+session.zh.md: b145334dec7483397a8cb6c41c50d3653d8f6972