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/core/settings_catalog.py

@@ -151,8 +151,11 @@ CATALOG: dict[str, SettingMeta] = {
     "llm_summary_model": SettingMeta(
         "llm_summary_model", "LLM (aipi)", "LLM summary model"
     ),
-    "llm_thinking_level": SettingMeta(
-        "llm_thinking_level", "LLM (aipi)", "Thinking level"
+    "llm_chat_thinking_level": SettingMeta(
+        "llm_chat_thinking_level", "LLM (aipi)", "Chat thinking level"
+    ),
+    "llm_summary_thinking_level": SettingMeta(
+        "llm_summary_thinking_level", "LLM (aipi)", "Summary thinking level"
     ),
     "stream_thinking": SettingMeta(
         "stream_thinking", "LLM (aipi)", "Stream thinking"