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`.

app/schemas.py

@@ -183,11 +183,20 @@ class ChatToolResultEvent(BaseModel):
 
 
 class ChatDoneEvent(BaseModel):
-    """Final SSE event of a chat turn: metadata for the finished answer."""
+    """Final SSE event of a chat turn: metadata for the finished answer.
+
+    Phase 113: ``related`` — the secondary related-doc tier (documents
+    that scored but did not clear the usefulness bar, LOCKED A2/A4). The
+    UI renders it as the de-emphasized "nearby docs" row — never a
+    citation chip — while ``sources`` stays the citation surface. The
+    field is ADDITIVE: old clients ignore unknown fields (PLAN §4 house
+    contract) and old frames without it parse with the default ``[]``.
+    """
 
     type: str = "done"
     deflected: bool
     sources: list[SourceRef]
+    related: list[SourceRef] = []
     suggestions: list[str] = []