own /effort: respawn-with-resume carrying --effort, picker UX (T-412)

Spike result (probed claude 2.1.175 over stream-json): there is NO
set_effort/set_thinking_effort control subtype — both are rejected. The
lever is the `--effort <level>` spawn flag (low/medium/high/xhigh/max;
settings.json effortLevel is the persisted default). So changing effort
restarts the process: respawn-with-resume keeps the conversation and
carries the flag — the same continuity /clear and /resume already rely on.

- SpawnSpec.effort → orchestrator appends `--effort <level>`.
- claude_pane: /effort <level> validates and respawns (toast explains the
  restart); bare /effort opens a picker; the pane re-applies its effort on
  every later respawn. Invalid level → local notice listing levels.
- ModelPickerCard generalised minimally (title + isCurrent predicate) so
  the effort picker reuses it; effort needs exact matching because `high`
  is a substring of `xhigh` and alias-containment would mis-mark it.
- SessionStatus.effort + StreamJsonSession.noteEffort: the wire never
  reports effort, so the spawner records what it set; status/sidebar read
  it from the normal status stream.
- Routing: effort moves from the TUI-only catalog to kClideOwnedCommands.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

lib/builtin/claude/src/stream_json_session.dart

@@ -162,6 +162,18 @@ class ModelOption {
   final String description;
 }
 
+/// Effort levels `claude --effort` accepts (probed against 2.1.175). There is
+/// NO set_effort control subtype (probed: rejected), so changing effort
+/// respawns the session with the flag — resume keeps the conversation (T-412).
+/// Expressed as [ModelOption]s so the /effort picker reuses the /model card.
+const List<ModelOption> kEffortLevels = [
+  ModelOption(value: 'low', displayName: 'low', description: 'fastest, minimal thinking'),
+  ModelOption(value: 'medium', displayName: 'medium', description: 'balanced'),
+  ModelOption(value: 'high', displayName: 'high', description: 'thorough'),
+  ModelOption(value: 'xhigh', displayName: 'xhigh', description: 'deeper reasoning'),
+  ModelOption(value: 'max', displayName: 'max', description: 'maximum thinking budget'),
+];
+
 /// Fallback picker entries for when the `initialize` response hasn't arrived
 /// (or carried no models): the stable aliases every claude build accepts
 /// (T-408). `default` resets to the CLI's configured model.
@@ -801,6 +813,11 @@ class StreamJsonSession {
     _items.add(AssistantTextMessage(uuid: 'local-${_localSeq++}', timestamp: DateTime.now(), isSidechain: false, text: text, synthetic: true));
   }
 
+  /// Record the effort level this session was spawned with (`--effort`,
+  /// T-412). The wire never reports effort, so the spawner tells the status
+  /// what it set; the status line / sidebar read it from [SessionStatus].
+  void noteEffort(String level) => _mergeStatus(SessionStatus(effort: level));
+
   /// Interrupt the running turn (the escape hatch for a runaway — D-78). Sends
   /// the `interrupt` control_request; claude cancels the current turn and ends
   /// it with a `result`, which clears [busy]. Safe to call when idle.