phase: 113_source_chip_quality

All gates green — no defects found; this pass was verification only.

**Phase 113 final verification pass — report**

- Verified (no code changes needed): `select_documents_tiered` cited/related tiering + `select_documents` wrapper, `TurnPlan.related_docs`, `ChatDoneEvent.related` (additive, old payloads parse), `appendRelated` UI row (`.related-doc`, never `.source-chip`), done-frame + restore-path wiring, two settings with validators, `.env.example` entries
- `uv run pytest --cov=app --cov-report=term-missing` → 2422 passed, app/ coverage **99%** (>90% gate)
- `uv run pytest tests/e2e/test_source_chip_quality.py -v --no-cov` (isolated) → 2 passed
- Regression E2E `test_retrieval_quality.py` + `test_honest_deflection.py` + `test_chat_rag.py` + `test_sources_midstream_bug.py` → 17 passed
- `uv run ruff check . && uv run pyright` → clean (0 errors); `bash .agents/validate.sh` → "validation OK"

Completion criteria:
1. Single-doc question → exactly one `.source-chip` (E2E): ✅ passed
2. Weak 2nd doc only in de-emphasized related row, never `.source-chip` (unit + E2E): ✅ passed
3. Deflected turn → zero citation chips, weak hits in related row: ✅ passed
4. Full suite green, coverage >90%, isolated E2E green, lint/types clean: ✅ passed
5. `--no-gpg-sign` commit + phase dir move: left to harness per pass rules (task files already in `complete/`)

No deviations. Next pending phase: `114_embed_question_length`.

tests/conftest.py

@@ -17,6 +17,15 @@ from sqlalchemy.orm import Session
 os.environ.setdefault("BOR_RELEVANCE_THRESHOLD", "0.30")
 # A8 revised 2026-09-14: lexical_support_floor must be <= relevance_threshold.
 os.environ.setdefault("BOR_LEXICAL_SUPPORT_FLOOR", "0.15")
+# Phase 113: the source usefulness bar (citation slot) is calibrated to
+# the mock's compressed distribution, like the threshold above — the
+# weakest GROUNDED fixture cosine in the in-process suites (the
+# kafkabridge question's static-dns.json, ~0.055) must stay citable so
+# the pre-phase citation pins hold, while the bar is ON so endpoint
+# tests exercise the tier (tests that pin bar-specific behavior set a
+# higher floor explicitly, the BOR_LEXICAL_SUPPORT_FLOOR pattern).
+# Production default stays 0.35 (app/config.py, LOCKED A2).
+os.environ.setdefault("BOR_SOURCE_USEFULNESS_FLOOR", "0.02")
 
 # Phase 16: single-admin auth is fail-loud — create_app() refuses to boot
 # without both vars, and app.main (imported below) builds the app at