docs: complete oq-promotion-sync — AGENTS.md current with Phase 1, add TN-12 tracker

- AGENTS.md architecture bullet: spec exists (present tense), OQ tracker
  authoritative; convention 16 de-hedged (shape pinned by ADR-004/005);
  alkcall version drift fixed (v0.4.x/v0.5.x -> v0.7.x per Cargo.toml);
  Phase 1-work bullet -> Phase 1 complete, Phase 2 in tasks/
- phase-0-findings.md: promotion note atop the Open Questions section
  pointing at docs/architecture/open-questions.md; convergence
  checklist's final item checked
- tasks: add architecture/oq-tn-12-tracker (external-trigger tracker for
  OQ-TN-12 deferred(scope), per sdd_process.md deferred-OQ two-halves
  rule); OQ-TN-12 Blocked-on text now references the tracker id
- tasks: oq-promotion-sync completed (scope grew: 3 folded stale
  AGENTS.md refs found during review + the TN-12 tracker)

Verified: taskgraph validate (13 tasks), grep sweep clean for stale
'not exist yet'/version-drift language, cargo test + cargo fmt --check

docs/architecture/open-questions.md

@@ -191,7 +191,8 @@ OQ-TN numbering. Format per `docs/sdd_process.md`.
   the seed shape (consumer + `register_openable` on the same
   connection) but does not exercise re-export; if one materializes,
   decide whether a composition helper belongs in this crate or is
-  assembly-layer wiring of the existing surface.
+  assembly-layer wiring of the existing surface. Tracker task:
+  `architecture/oq-tn-12-tracker` (tasks/architecture/).
 - **Cross-references**: OQ-TN-05, ADR-004, alkcall ADR-042 (relay)
 
 ### OQ-TN-13: UDP truncation semantics at the codec boundary