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`.

.env.example

@@ -33,9 +33,11 @@ BOR_EMBEDDING_DIM=768             # verified 2026-08 via scripts/llm_probe.py
 BOR_STREAM_THINKING=1             # stream the model's thinking as `thinking` SSE events (0 to suppress)
 
 # --- RAG tuning ---
-BOR_TOP_N_DOCS=2
+BOR_TOP_N_DOCS=2                  # CEILING for the cited tier, not a quota (phase 113): a single strong doc yields one citation
 BOR_RELEVANCE_THRESHOLD=0.62      # answer when best cosine >= this OR an FTS hit corroborated by cosine >= lexical_support_floor; else honest deflection
 # BOR_LEXICAL_SUPPORT_FLOOR=0.35  # cosine floor for FTS hits to flip HIGH (A8 revised 2026-09-14); 0 <= floor <= relevance_threshold
+# BOR_SOURCE_USEFULNESS_FLOOR=0.35 # cosine bar for a citation slot (phase 113): a doc earns done.sources only when its best-chunk cosine clears it; 0 <= floor <= relevance_threshold; 0 = no bar
+# BOR_RELATED_MAX_DOCS=2            # cap on the related-doc tier in the done frame (phase 113: the UI's de-emphasized "nearby docs" row, never a citation chip); 0 = no related docs
 BOR_MAX_OUTPUT_TOKENS=32768       # max answer length in tokens (answers must not be cut off)
 BOR_STEERING_MAX_CHARS=8000       # char budget for the <tuning> (steering notes) prompt section
 BOR_SUMMARY_MAX_CHARS=12000       # cap on document content sent to the lite summary model (phase 30)