tui: async REST api client — stop blocking the event loop (Etap 3) ...

The terminal client's REST helpers were synchronous (httpx.Client); every
caller inside the Textual event loop (attach/switch/resume/profile/stop) blocked
the whole TUI for the duration of each network round-trip — the spinner froze,
input stopped responding, the screen did not repaint. Move the network layer to
async and a shared pooled client:

- api.py: all 7 helpers are now `async def` over a single lazily-created
  httpx.AsyncClient (connection pooling) — awaits yield the loop while a request
  is in flight, so the TUI never blocks on the network.
- tui_app.py + commands/builtin.py: every `api.*` call site is now `await`-ed
  (all already ran in async workers / execute). _stop_stream_worker drops the
  dead `iscoroutine` check (api.stop_session is async, the await is real).
- cli.py: _resolve_session_id and _handle_command await api.*; _run_raw wraps
  the resolve + run in asyncio.run(_run_raw_async) so the sync click entrypoint
  stays unchanged. Removed the now-unused _run_one_shot wrapper.
- sessions_picker.on_mount: list_sessions runs in a worker (run_worker) instead
  of blocking on_mount — a slow/unreachable backend no longer hangs the modal;
  the input is focusable immediately and the list populates when the request
  returns.

Tests: every api mock across 6 client test files is now an `async def` fake
(test_tui_app, test_chat_panel, test_sessions_picker, test_terminal_client,
test_tui_export, test_input_box); the sessions picker tests use an async
_raise_not_found helper for the 404 path. Full suite: 939 passed, 1 skipped.

Isolate sub-agent todo + render live todo in TUI side panel ...

Phase 1 — sub-agent todo isolation (backend):
- Add current_todo_session_id ContextVar; subagent_runner scopes it to the
  sub-agent's ephemeral run id so its auto-populated plan and todo updates
  land in an isolated KV row instead of clobbering the parent session's todo
  (which the parent's goal-anchoring reads every iteration).
- todo._sid() and planning.set_tasks prefer current_todo_session_id; the
  parent run leaves it unset, so all existing todo consumers (anti-stall,
  goal anchor, get_progress_message) behave exactly as before.

Phase 2 — live todo in the TUI right column:
- TodoUpdated event + emit it from the agent loop after planning auto-populate
  and after each tool-execution turn.
- GET /sessions/{id}/todos reads the parent session's todo KV row (explicit
  user_id/session_id, optional injected kv).
- api.get_todos + TodoList/TodoPanel widgets: status-coloured markers
  (pending dim, in_progress accent+bold, done success, failed error, skipped
  dim), progress header, scrollable panel below the auto-height info block.
- Hybrid delivery: REST seeds the panel on attach/switch, todo_updated WS
  events update it live.

Sub-agent todos as nested sub-lists is deferred to a later phase.

Co-Authored-By: Claude <noreply@anthropic.com>

tui: show the currently-served model in the status panel ...

The status panel's Model line was fed the global ollama_default_model, not the
session/profile model, and the server never told the client which model
actually served a call. Now:

- Backends stamp the resolved model onto LLMChunk (first chunk) / LLMResponse.
  The fallback backend reports the model that survived its server+model
  priority list (may differ from the profile's first choice).
- New ModelInfo event ({"type":"model_info","model":...}) emitted once per
  turn from agent._consume_stream, re-emitted only when the model changes
  across iterations. Additive WS event — old clients ignore it.
- TUI: attach_session/switch fetch the profile's configured model (first of
  profile.model) via api.get_profile_model so the panel shows a value before
  the first request; model_info then refines it to the actually-served model.
  Not forwarded to the chat panel. raw CLI prints "[model] ...".

Co-Authored-By: Claude <noreply@anthropic.com>

Navi Code: Phase 2 — CLI terminal client, tests, docs ...

- Add clients/terminal package: config, state, REST API wrappers, WebSocket
  client, renderer, and click-based interactive CLI.
- Wire navi-code console script via pyproject.toml.
- Add unit and WebSocket integration tests for the terminal client.
- Update docs/profiles.md, docs/config.md, README.md with navi_code profile
  and default-profile instructions.
- Add docs/navi_code.md setup guide and docs/navi_code_cli.md usage reference.
- Fix lint in new test files and test_auth_disabled.py.

Tested: 459 passed, 1 skipped (excluded unrelated websocket test).

Co-Authored-By: Claude <noreply@anthropic.com>