Require a token for writes and quarantine what nobody vouches for

Sixteen mutating routes now refuse a caller who cannot present the token the
server started with; queries stay open, because a question is not a write. The
environment variable is ELY_EYE_AUTH_TOKEN, following the repo's env_prefix
convention — the shorter name I reached for first returned 403 where the smoke
expected 401, and the server printed the reason.

Words from a stranger are quarantined on the way in: an HTTP upload is
third_party by definition, and a sentence carrying an instruction-shaped phrase
is quarantined whoever wrote it. A quarantined atom stays findable and stays out
of the compiled context until a second, live, unquarantined source agrees with
its rarest words. Corroboration is computed at read time because it is a
property of the corpus now, not of the moment a memory was written; it is
term-level, and the docstring says so.

forget now erases the source row and the compiled contexts beside the atoms, so
a forgotten memory leaves nothing that can still speak. The semantic cache key
carries a store revision, which fixes a real staleness: a context compiled
before new evidence arrived kept its old quarantine decision forever.

bench.audit --product still pointed at evals.py, which the p1-6 split moved into
backend/src/ely_eye/proofs/. It failed fast, but the anti-self-justification
rule had quietly stopped auditing the product; it now walks the package, and a
test pins that the package exists and holds no re-roll.

Gates: pytest 306 passed; ruff clean; mypy cold cache 24 errors in 9 files, the
recorded baseline, net zero; pyright 0 errors on the 23 backend files and the 2
bench files; go build/vet/test and gofmt clean; npm run build 221.39 kB with
eslint exit 0; bench/filesize_check clean; bench.audit --product clean over 31
harness files; scripts/mcp_write_smoke.sh PASS with the gate live across two
servers and the MCP child.

backend/tests/test_memory_api.py

@@ -14,10 +14,10 @@ KEYS = "我们的钥匙放在玄关抽屉里"
 
 
 @pytest.fixture
-def client(tmp_path: Path, monkeypatch: pytest.MonkeyPatch) -> TestClient:
-    settings = Settings(home=tmp_path, default_holder="wife")
+def client(tmp_path: Path, monkeypatch: pytest.MonkeyPatch, write_token: str) -> TestClient:
+    settings = Settings(home=tmp_path, default_holder="wife", auth_token=write_token)
     monkeypatch.setattr(api_module, "get_settings", lambda: settings)
-    return TestClient(api_module.create_app())
+    return TestClient(api_module.create_app(), headers={"Authorization": f"Bearer {write_token}"})
 
 
 def test_post_memory_stamps_the_holder_the_server_knows(client: TestClient) -> None: