docs(architecture): ADR-015 — manage grant tier + repo-op gate, OQ-16 identity namespace

Resolves review 001 finding A-1 (critical): ADR-012 §3's "scope
git:admin OR ownership" gate is not expressible in alkcall's
AccessControl (AND-composition). Resolution is the review's option (a)
shape with the OR-term generalized: the per-repo grant action set gains
manage, authorize(record, identity, read|write|manage) becomes the
single policy function for git access and repo administration, and the
delete/update/get gate is admin scope OR manage grant (handler-side,
generic FORBIDDEN, unknown-repo = unauthorized per ADR-008). Repo
create seeds the creator's {read, write, manage} grants —
administration is grantable, so collaborators/bots/app-compiled roles
work without global scopes. Ownership stays as alkcall spawn-tracking
(mint at create unchanged); "ownership never implies git access" is
superseded.

- ADR-015 (new): manage grant tier, op gate, flat-grants-as-replication-
  substrate, opaque grant-key rule
- ADR-011: action set + policy domain amended, references updated
- ADR-012 §3: gate table replaced, two-tier paragraph superseded
- backend.md/doors.md/overview.md: gate + grant restatements, ADR tables
- OQ-16 (new, deferred(scope)): grant-key identity namespace —
  globally-comparable ids for cross-assembly/replicator grant state;
  tracker task tasks/architecture/oq-16-grant-identity-namespace.md
- review 001: A-1 marked resolved (ADR-015)
- vision.md: supersession notes (Internal-ops framing, v1 grant set)

Verification: cargo test, clippy -D warnings, fmt --check, doc --no-deps
all clean.

docs/reviews/001-architecture-pre-decomposition-review.md

@@ -758,7 +758,7 @@ criticals are ADR-writing work, not code):
 
 | ID | Finding | Recommended fix | Effort | Risk | Status |
 |----|---------|----------------|--------|------|--------|
-| A-1 | op-gate OR not expressible in `AccessControl` | new ADR (or ADR-012 §3 amendment): handler-side two-tier check, create keeps static scope gate | small | none | open |
+| A-1 | op-gate OR not expressible in `AccessControl` | new ADR (or ADR-012 §3 amendment): handler-side two-tier check, create keeps static scope gate | small | none | **resolved (ADR-015)** — option (a) shape with the OR-term generalized to the `manage` grant |
 | A-2 | `async fn` traits not dyn-compatible | ADR-012 §1 + backend.md amendment: `#[async_trait]`; add `async-trait = "0.1"` to manifest | small | none | open |
 | A-3 | native preamble / service dimension unpinned | new ADR: open-op params `{repo, service}`, session tuple + stateless entry gain the service selector, `GitAdapter` preamble pinned | moderate | wire-format (freeze inventory) | open |
 | A-4 | done-round boundary set unverified | ADR-014 §2 + transport.md clause: boundary = `common_haves`-filtered haves | trivial | none | open |