ADR-012: forked-substrate design — contract-blind boundary, fidelity posture, port deltas

Follow-through on OQ-06/ADR-011: pin the fork's structural decisions
(alkstore-substrate as a vendored path-dep crate, contract-blind API
boundary with contract formulas computed engine-side and pinned
equivalent by the contract suite, keep-the-kept-half API fidelity for
cheap cherry-picks, the W-1/W-2/dead-man's-switch/W-4 port deltas
decided per item, bootstrap re-keying off error-string matching, no
rename migration, deliberate upstream tracking).

Consistency sweep across the doc set for the fork: annotate ADR-003/
005/009/010 and core-contract for superseded ownership facts, fix
schedule-storage table naming (ADR-009 §5, queues.md), re-key ADR-010
§6's notifications hygiene to the at-attach cap the fork scope
realizes, add OQ-11 (scaffold-time residue), and complete both ADR
indexes. Independent review: 0 critical, warnings addressed.

docs/architecture/decisions/006-wake-and-delivery-contract.md

@@ -126,4 +126,7 @@ consumer-inventory-row-gated extension — not assumed now.
 - [ADR-007](007-transactional-seam.md) — commit-atomicity's mechanism
   (the `*_tx` seam).
 - [core-contract.md](../core-contract.md) — the spec carrying this
-  contract's full surface.
+  contract's full surface.
+[ADR-004]: 004-postgres-driver.md
+[deployment.md]: ../deployment.md
+[engine-postgres.md]: ../engine-postgres.md