docs: open Phase 1 — architecture spec set over the Phase 0 evidence

docs/architecture/ now exists: README index, overview, five component
specs (core-contract, engine-sqlite, engine-postgres, queues,
deployment), ADR-001..007 carrying the Phase 0 resolved decisions
(crate split, feature scope, per-engine drivers, dependency
ownership, wake contract, tx seam), and the centralized
open-questions tracker promotion: OQ-ST-01..08 mirror to OQ-01..08
one-to-one with statuses/resolutions carried; new Phase 1 questions
append (OQ-09 scheduler collapse, OQ-10 contract versioning).
Open Phase 1 work: OQ-04 contract pinning (high), OQ-05 queue
semantics depth (high), OQ-06 honker-core quality read (high;
fork-trigger gate), OQ-08 capability surface, OQ-09, OQ-10.

Erratum fixed in phase-0 OQ-ST-04 (thread-affinity friction is
SQLite-side, previously garbled as pg-side) and a stale scheduler-
boundary pointer corrected in consumer-inventory.md. Two review
passes run (findings: OQ-promotion numbering faithfulness, ADR
back-reference sync) — all critical/warning findings resolved.

docs/research/consumer-inventory.md

@@ -210,7 +210,11 @@ none of them yet.
   features as contract candidates; the ambiguity found in the
   inventory (queues vs scheduler boundary; streams' absent consumer;
   rate limits' alternative mechanism) is input to which parts of the
-  honker-rs surface become contract versus cut.
+  honker-rs surface become contract versus cut. *(Correction
+  2026-10-04, promotion pass: the scheduler-collapse question was
+  OQ-ST-05/06 territory in this line's original framing and is now
+  tracked as OQ-09 in `docs/architecture/open-questions.md` — not
+  OQ-ST-04/02 as this line previously garbled.)*
 
 ## The consumer list, honestly bounded