phase: 178_split_thinking_levels

## Phase 178 — final verification pass: 100% green

**Verified (all 5 tasks complete in `complete/178_split_thinking_levels/`):**
- `config.py` rename (`llm_chat_thinking_level` default `low`) + new `llm_summary_thinking_level` (default `""`); two `CATALOG` rows; `.env.example` replaced; no stale old-key references (only intentional negative pins in tests)
- Wire split: `chat_stream()` → chat level, one-shot `chat()` → summary level (absent `extra_body` when empty); per-turn line reads chat level only

**Gates:**
- `uv run pytest -k "config and thinking" -v` → 7 passed (defaults + env overrides both knobs)
- `uv run pytest` (unit + integration) → 4170 tests, exit 0; `--cov=app` → **99%** (>90% ✓)
- `uv run ruff check .` clean; `uv run pyright` clean
- `uv run pytest tests/e2e/test_split_thinking_levels.py -v --no-cov` → 3 passed in isolation
- `test_admin_settings_panel.py` + `test_admin_settings_layout.py` → 17 passed in isolation

**Completion criteria:** all 6 test/doc criteria ✅ (admin GET lists both keys, old key gone — integration + E2E pins); commit + phase-dir move = harness's job.

**Documentation:** README.md — both new env vars correctly documented in the LLM (aipi) table with defaults/wire-mapping/off-rule, defaults match `config.py`, all `.env.example` vars covered: verified consistent, no changes needed. AGENTS.md — all referenced files/commands verified to exist, no phase-178 impact (no UI code change, A4): verified consistent, no changes needed.

**Decisions:** none required — no live changes made (E2E booted its own app subprocess against the existing DB).

**Next pending phase:** none — 178 is the last phase in `todo/`.

app/api/chat.py

@@ -15,8 +15,9 @@ turn's thinking is counted in the per-turn log line
 (``thinking_chars=N``); ``BOR_STREAM_THINKING=0`` suppresses the
 ``thinking`` frames (the pieces are still counted). The per-turn log
 line records ``thinking=<level>`` (the effective
-``BOR_LLM_THINKING_LEVEL``, trimmed, ``-`` when empty) before
-``thinking_chars`` (phase 172, A6).
+``BOR_LLM_CHAT_THINKING_LEVEL``, trimmed, ``-`` when empty) before
+``thinking_chars`` (phase 172, A6; phase 178, A5 — the **chat**
+level; the one-shot summary level never appears on the line).
 
 Honesty gate (A8, revised 2026-09-14): LOW — deflection — only when
 ``best_cosine < BOR_RELEVANCE_THRESHOLD`` **and** (``fts_hits == 0``
@@ -1286,7 +1287,11 @@ async def chat(
                     settings.relevance_threshold,
                     plan.deflected,
                     source_paths,
-                    settings.llm_thinking_level.strip() or "-",  # phase 172 (A6)
+                    # phase 178 (A5): the effective chat thinking
+                    # level, trimmed, `-` when empty — the level this
+                    # turn ran at; the summary level is a one-shot
+                    # concern and gains no field here.
+                    settings.llm_chat_thinking_level.strip() or "-",
                     thinking_chars,
                     holder.tool_calls,
                     holder.rounds,