phase: 82_security_headers

All completion criteria verified green — no defects found, nothing to fix. Final report:

**Phase 82 (security headers) — final verification pass: all green**

- Verified prior-run implementation: `app/core/security_headers.py` (pure-ASGI, header-only, exact A1 CSP), registration in `app/main.py` after `configure_caching` (outermost), unit/integration/E2E suites.
- Deviation confirmed sound: `data:`-URI favicon (blocked by locked CSP) → static `frontend/assets/favicon.svg` in 5 templates + Containerfile `cp`; SVG element byte-identical to the old data-URI (verified programmatically); serves 200 with all three headers.
- Curl check (server booted like e2e conftest, log: `/tmp/curl_security_headers_final.log`): `/`, `/api/health`, `/assets/styles.css`, `/nope` (404) → all three headers, CSP exactly `default-src 'self'; base-uri 'none'; frame-ancestors 'none'`.
- `uv run pytest tests/unit/test_security_headers.py tests/integration/test_security_headers.py -v --no-cov` → 13 passed (incl. SSE byte-identity pin).
- `uv run pytest tests/e2e/test_security_headers.py -v --no-cov` (isolated) → 2 passed (headers + zero CSP violations + painted page).
- SSE tripwire `uv run pytest tests/e2e/test_chat_rag.py -v --no-cov` → 3 passed.
- `uv run pytest --cov=app --cov-report=term-missing` → 1665 passed, app/ 99% (>90%); `uv run ruff check . && uv run pyright` → clean (0 errors).
- `git diff --stat` limited to phase-82 files + the two documented deviations (favicon set, `tests/unit/__init__.py`); no `pyproject.toml`/`uv.lock`/JS diffs.
- Commit + phase-dir move left to the harness per pipeline rules (not executed by me).

Next pending phase: `83_chat_save_payload_limits`.

Containerfile

@@ -25,6 +25,7 @@ RUN mkdir -p /out/assets \
     && esbuild ./assets/markdown.js --minify --outfile=/out/assets/markdown.js \
     && esbuild ./assets/styles.css  --minify --outfile=/out/assets/styles.css \
     && cp -r ./assets/themes /out/assets/themes \
+    && cp ./assets/favicon.svg /out/assets/favicon.svg \
     && cp ./index.html ./document.html ./login.html ./shared.html ./doc-edit.html /out/
 
 # ---------- Stage 2: python dependencies ----------