fix(P07): final review — CORS PUT, WS origin gate, ingest leak+O(n²), symlink escape, retry leak, doc-reality gaps

---ci---
phase: 7
milestone: v0.3
status: review
lessons:
  - P0 CORS: allow_methods lacked PUT while the build surface writes files with PUT — every cross-origin Save failed preflight; pinned with tests/api/test_cors.py
  - P0 ingest leak: queue-overflow flood path returned without the disconnect sentinel, parking the drainer forever (one leaked task-set per flooded trace); sentinel now always enqueued, real-server regression test added
  - P1 perf: flood cap counted rows via len(get_trace(...)) — O(trace) per append, O(n²) per session; TraceStore.count() (COUNT(*)) added and wired
  - P0 security: file routes followed exec-planted symlinks out of the workspace bind; _resolve_in_workspace refuses escapes (422), read/write now 404 on unknown sandboxes (was 500)
  - P1 security: WS ingest accepted any browser Origin (CORS middleware does not cover WS); localhost dev origins + no-Origin (capture agent) allowed, others 1008
  - P1 correctness: use-sandbox-session leaked a created sandbox on any mid-start failure (per-learner cap 1 → all retries 429 forever); failed starts now destroy what they created
  - P2 testing: reconnect-flush test killed mid-burst (nondeterministic under load, reproduced on pre-change code); now waits for server-side observation of the pre-kill burst — the underlying one-line replay-margin/ACK gap is documented for v0.4
  - maintainability: grading-store/templates/grading.ts docstrings claimed grading is variant-blind (stale pre-P4 text) — updated; ARCHITECTURE.md referenced nonexistent voice/openai_audio.py; dead if TYPE_CHECKING: pass blocks removed
---/ci---

apps/ai-service/ai_service/variants/templates.py

@@ -71,11 +71,11 @@ class RubricAnchors(BaseModel):
     for this template, so two variants of one template are held to the
     same bar regardless of which slot values a learner drew. The a-5
     envelope test (tests/variants/test_generator.py) binds variants to
-    these bands in code. Shipping them into the grader prompt context is
-    the P4 must-have follow-up tracked for final review: grading is
-    variant-blind in the current wiring (engine.py stamps
-    variant_seed=None), so today the anchors gate variant fairness in
-    tests only — not yet in the LLM prompt.
+    these bands in code, and — since Phase 4 (MH#4) — the grading engine
+    ships this envelope into the grader prompt
+    (grading/engine._anchors_context) and stamps the variant seed on the
+    GradeRecord, so the anchors gate variant fairness in BOTH tests and
+    the live rubric.
     """
 
     model_config = ConfigDict(frozen=True)