docs(tasks): post-remediation sweep — 4 follow-up tasks

Found in the sweep of completed review-001 remediation:
- /publish schema validation fails open on compile error + recompiles
  per request (remediation-introduced, routes.rs:254-268)
- OAI-06 loud-degradation unblocked and still open (HTTP_0 marker)
- HY-06 ExponentialBackoff in public API + COV-02 mTLS success path
  both unblocked post client-config rework
- HY-02/04/11 publish-prep docs gate (104 missing-docs warnings
  re-measured)

Also flagged, not tasked here: WS-12 (alkcall demux 4 GiB discard
alloc) was never actually filed in alkcall's consumer-findings-ledger —
only CF-001 is there. File it when next touching alkcall.

taskgraph: validate clean (42), no cycles

tasks/gateway/review-001-publish-schema-validation-robust.md

@@ -0,0 +1,67 @@
+---
+id: review-001-publish-schema-validation-robust
+name: Fix /publish schema validation fail-open + per-request recompilation (post-remediation)
+status: pending
+depends_on: []
+scope: narrow
+risk: high
+impact: component
+level: implementation
+tags: [gateway, review-001, follow-up]
+---
+
+## Description
+
+Follow-up to review-001-gateway-publish-semantics (GW-01): the landed
+fix compiles the op's `publish_schema` **on every `/publish` request**
+(`src/gateway/routes.rs:254-268`) and, when compilation fails, logs a
+warning and proceeds with **no validation** — chunks flow to the handler
+unvalidated. Two remediation-introduced problems:
+
+- **Fail-open on compile failure** — this reintroduces, conditionally,
+  the exact transport-dependent invariant GW-01 closed: a handler that
+  registered a `publish_schema` (or a remote import whose schema is
+  un-compilable by jsonschema 0.46's dialect) silently receives
+  arbitrary JSON over the HTTP path that the wire path would have
+  aborted. A registry with one broken schema becomes an unvalidated
+  ingest path with only a `tracing::warn` as the tell.
+- **Per-request compile cost** — `jsonschema::options().build()` on the
+  hot path is CPU + allocation per publish call; a hostile or merely
+  busy caller multiplies it.
+
+Fix direction (implementer's choice on mechanism): compile **once per
+registration** — cache the compiled `Validator` (or the compile error)
+against the op in the gateway state, invalidated on re-registration —
+and make compile failure **loud and closed**: the request path surfaces
+a server-fault (500, `INTERNAL`-class with the compile error logged at
+error level), never a silent skip. Consider whether adapters can reject
+un-compilable `publish_schema` values at import/registration time so
+the failure lands before any traffic (adapter-side validation where the
+schema originates), with the gateway cache as defense in depth.
+
+## Acceptance Criteria
+
+- [ ] Compiled validator (or error) cached per registration; no per-request recompile (test: compile count / perf shape not asserted, but code path is registration-keyed)
+- [ ] Un-compilable `publish_schema` → request fails loudly (500/INTERNAL, error logged), chunks never flow unvalidated (test)
+- [ ] Schema re-registration (hot reload) picks up the new schema (test)
+- [ ] A `publish_schema`-registered Pub op still rejects an invalid chunk (existing GW-01 gate stays green)
+- [ ] `cargo test` and `cargo clippy --all-targets -- -D warnings` pass
+
+## References
+
+- docs/reviews/001-initial-implementation-review.md (Part C, GW-01)
+- tasks/gateway/review-001-gateway-publish-semantics.md (the landed fix + rationale)
+- src/gateway/routes.rs:254-268 (the fail-open)
+
+## Notes
+
+> Agent fills during implementation. Found in the post-remediation
+> sweep — not a Review 001 finding itself. Fail-open is the priority
+> half; caching is the efficiency half. Registration-side (adapter)
+> rejection at import is the preferred end state if alkcall's
+> registration surface allows observing `publish_schema` at
+> HandlerRegistration time.
+
+## Summary
+
+> Filled on completion.