docs: step-3 rewrites — OQ-39/40 resolved, C-08 closed, channel-operations.md put/control/resources contracts, review 010/011 closed with the S-01 sketch corrected

- open-questions.md: OQ-39 → ADR-052, OQ-40 → ADR-053 (resolutions replace
  the deferred-until-needed posture)
- channel-operations.md: the put contract (initiator allocates + streams,
  reserved input key, one response, acks-in-result sentence), the control
  routing (ADR-052), the enumerator aggregation (ADR-053), the
  connection-owner paragraph's pub-era correction, the ADR table rows
- ADR-051 §6: PubTypedOpen → the put translation; ADR-047's 2026-09-06
  amendment records its era honestly (the dynamic half is now ADR-053)
- review 010: all four findings resolved (with the S-01 sketch correction
  so the published record stops carrying the wrong-graph reading)
- review 011: closed (all seven pins implemented + gates landed)
- review 001 C-08: resolved note (odd/even + adopt, implemented)
- AGENTS.md: the 'Stub Guard' section — the not_implemented grep is part
  of cargo test; the registration invariants and the implement-or-stop
  ruling are release-blocking

Verified: cargo test (696+guard), clippy -D warnings, fmt, doc clean.

AGENTS.md

@@ -213,6 +213,28 @@ cargo clippy --target wasm32-unknown-unknown -- -D warnings
 cargo semver-checks check-release             # before a release
 ```
 
+## Stub Guard (release-blocking)
+
+Four registered-but-always-failing stubs shipped across nine published
+versions (reviews 010/011). This class is now release-blocking in both
+directions:
+
+1. **Test guard**: `cargo test --test stub_guard` (part of `cargo
+   test`) fails if the string `not_implemented` appears anywhere in
+   `src/`. A "loud failure" stub is still a stub.
+2. **Registration-time invariants** (ADR-047 amendment 4 §4.8): a
+   marked (`channel_open`) spec refuses the generic registration path
+   (`OperationRegistry::register`, `CallConnection::register_imported`,
+   `op/register`) and refuses `publish_schema`; the sanctioned
+   registrations are the channel wrapper family
+   (`register_openable*`, `register_pub_openable`,
+   `register_relay_openable`).
+3. **The ruling**: implement-or-stop-advertising before any publish.
+   The only permitted deferral statement is "not this session" — never
+   "next version", "not v1", or any bucket that parks a decision on an
+   unknown future release. Every handler that registers on a
+   discoverable surface must be capable of succeeding.
+
 ## Architecture Context
 
 - `docs/architecture/` — the authoritative spec. Read it before