docs: consumer inventory answers OQ-ST-01; phase-0 consumes it

consumer-inventory.md: per-feature scope synthesis over the paused
consumers' written artifacts (alkfs phase-0, alkgit architecture,
alkblobs ADRs, alknet-filesystem POC) — dissolves the circular
'deferring to consumers who can't run until we exist' framing.
notify/locks pinned-or-documented (alkfs invalidation + writer coord,
alkblobs fleet sweeper); queues/outbox documented (alkfs sync outbox,
alkblobs embedder-owned cadence); scheduler documented-thin; streams/
rate-limits/result-storage have no named consumer — kept per working
posture with cut flags, to revisit before implementation.

phase-0.md: OQ-ST-01 answered by the inventory; OQ-ST-02 narrowed
(uniform feature family across engines favors single-crate shape);
OQ-ST-07 sharpened (no consumer needs the loadable-extension surface —
cut-only decision); OQ-ST-04 contract-pinning scoped to inventory rows;
plan step 1 marked done; references extended.

AGENTS.md: architecture context gains the inventory with its
add-a-row-before-assuming rule.

AGENTS.md

@@ -112,6 +112,10 @@ coordinator runs.
   art, open questions (OQ-ST-01..NN), the POC register, and (eventually)
   the converged recommendation. Read it before any non-trivial work in
   this repo.
+- `docs/research/consumer-inventory.md` — the per-feature scope
+  synthesis answering OQ-ST-01 from the paused consumers' documents.
+  New consumer needs get a row there *before* any scope decision
+  assumes them.
 - `docs/sdd_process.md` — the SDD process. Phase 0 in progress;
   `docs/architecture/` does not exist yet.
 - The SDD process and agent defs were copied from downstream projects