fix review findings: sync stale v1/removed-event doc references

Codex's re-confirmation pass verified both blocker fixes correct but found
doc/comment drift the fix commit missed:

- session/index.ts + session/README.md: "minimal v1 header" → "minimal header
  (stamped with the current SESSION_FORMAT_VERSION)" — the version is 0, not 1.
- session/index.ts deriveMessages comment listed "usage, and errors" as trace
  data — those standalone events no longer exist; only boundaries + chunks are.
- session-persistence RFC: "no v1 migration" → the pinned-v0 pre-release stance.
- collapse-trace-only RFC format-version note: reframed off the "bump the
  version and reject" wording (which now reads as the OTHER AGENTS.md stance)
  onto the pinned-0 unstable stance the session log actually uses.
- agent-loop/loop.ts finishError JSDoc: "with a logged `error` event" → the
  failure is recorded on turn/end.reason (no standalone error event).
- acp/acp-feature-support.md (two spots): usage is recorded on assistant/message
  now, not as standalone internal usage events.
- Regenerate the cordis catalog (finishError JSDoc line shift).

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

@@ -38,8 +38,8 @@ function toError(error: unknown): CodedError {
  * caller's try/catch), OR end the stream with a finish-error/aborted chunk
  * (the only option for adapters that can't throw mid-stream, e.g.
  * library-backed ones). This translates the latter into a thrown step error
- * so the turn ends error/aborted with a logged `error` event, never as a
- * normal `completed` assistant message.
+ * so the turn ends error/aborted (the failure recorded on `turn/end.reason`),
+ * never as a normal `completed` assistant message.
  *
  * `FinishReason` is merge-extensible (plugins/adapters can add `kind`s), so
  * the switch handles the known terminal-failure kinds and treats every other