tui: handle terminal lifecycle events + status-bar count (Etap 4) ...

terminal_opened/output/closed WS events used to fall through to ChatModel's
unknown-event path (raw dict dumped into chat). Now they feed a dedicated
terminals state and a status-bar count, with no chat bubble:

- ChatModel: terminals dict (name → {description, pid, background, status,
  output_tail, closed}) updated by terminal_opened/output/closed in
  handle_ws_event (return None — no chat item). open_terminal_count property;
  seed_terminals(summaries) populates from a REST list (on attach). output_tail
  capped at 200 lines.
- tui_app.on_ws_event: a terminal-events branch forwards to the model (no _sync
  walk — background output can be frequent) and updates the StatusPanel count.
  attach_session seeds via api.list_terminals and sets the count (graceful 0 on
  failure).
- StatusPanel: the "Ctrl+P palette | /help commands" hint line is replaced with
  a live "Terminals: N" count (set_terminals_count). Key combos still live in
  the bottom StatusBar.
- Tests: mock_tui_api fixtures across 5 client test files gain an async
  fake_list_terminals so attach_session never hits a real network in tests.

Tests: ChatModel opened tracks state (no bubble) / output appends tail / unknown
ignored / closed decrements count / seed from REST; tui_app terminal events
update the status count with no chat bubble. Full suite: 988 passed, 1 skipped.

Plan: docs/terminal_tool_plan.md — Etap 4 of 5.

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.

Navi Code TUI: unify session commands on shared workers; /switch hybrid ...

Route /new, /sessions, and /switch through shared app-side logic instead of
each command reimplementing the switch path:
- _open_sessions_picker(): pushes SessionsPickerScreen and wires the select
  callback to _switch_session_worker / _create_new_session_worker. Both
  /sessions and /switch (no/ambiguous arg) use it.
- /new -> _create_new_session_worker (was: inline create + attach + clear).
- /switch <prefix>: resolve to a single navi_code session (exact id, then
  prefix match) and switch directly via _switch_session_worker; no/ambiguous/
  unknown arg opens the picker pre-filtered to what was typed. This removes
  the latent clear()-after-attach bug from the old SwitchCommand (clear erased
  the history that attach_session had just replayed).
- SessionsPickerScreen gains initial_query to open pre-filtered.

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

Navi Code TUI: sessions picker for /sessions (navi_code, full switch) ...

Replace the chat-printed session list with a modal picker:
- SessionsPickerScreen lists only navi_code-profile sessions (filtered by
  settings.default_profile_id), with a filter input, a top "✚ New session"
  row, and the current session marked. Up/Down + Enter to pick, Esc cancels.
- /sessions pushes the screen. Selecting an existing session runs
  _switch_session_worker (persist via StateManager + attach_session, which
  replays history and restarts the WS bridge — no chat_panel.clear() after,
  since load_history already replaces the chat and clearing would erase the
  replayed history). The "New session" row runs _create_new_session_worker.

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