docs: tidy phase-0 corrections, pin reference revisions by path+rev

- complete the dangling honker prior-art sentence; fold the pg_notify
  posture into the interface-finding paragraph instead of the
  'restated conclusion' trailing paragraph
- reference checkouts are read freely but not for direct dependency
  use; published versions unless vendored/forked (alksocks precedent)
- pin honker @ f4e53c6 (russellromney/honker) and pgboss-rs @ 98f7d9e
  by path+revision per AGENTS.md §3
- reflow one hard-broken hyphen in the honker-rs limitations list

AGENTS.md

@@ -58,10 +58,13 @@ not change `git config`, skip hooks, or use `git commit -i`.
    `docs/research/phase-0.md` until Phase 1 promotes them to
    `docs/architecture/open-questions.md`. Numbering is stable — never
    renumber; append.
-3. **Reference read-only checkouts by path and revision.** The external
-   references for this crate (`/workspace/honker`,
-   `/workspace/pgboss-rs`) are read-only reference checkouts of
-   third-party projects. Note the checkout state when your findings
+3. **Cite reference checkouts by path and revision.** The external
+   references for this crate (`/workspace/honker` @ f4e53c6,
+   `/workspace/pgboss-rs` @ 98f7d9e) are reference checkouts of
+   third-party projects — read freely, but never wire the checkout
+   itself into our code. Use the published version unless we vendor or
+   fork it (alksocks' fast-socks5 precedent); if a fork is warranted,
+   forking is normal work. Note the checkout state when your findings
    depend on code specifics; licenses and provenance get recorded when
    we adopt code, not while only reading.
 4. **POC code stays out of this repo** until Phase 1 adopts it. A POC