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/session_orchestrator.dart

@@ -49,6 +49,7 @@ class SpawnSpec {
     this.team = false,
     this.memberName,
     this.forkSourceSessionId,
+    this.effort,
   });
 
   final String id;
@@ -81,6 +82,12 @@ class SpawnSpec {
   /// Takes precedence over [resume]/[sessionId] for arg selection.
   final String? forkSourceSessionId;
 
+  /// Effort level passed to `claude --effort` (low/medium/high/xhigh/max,
+  /// T-412). Null spawns without the flag — the CLI uses its configured
+  /// default (settings.json `effortLevel`). No set_effort control subtype
+  /// exists, so changing effort means respawn-with-resume carrying this.
+  final String? effort;
+
   /// Whether this spec spawns a forked session.
   bool get isFork => forkSourceSessionId != null;
 }
@@ -238,7 +245,13 @@ class ClaudeSessionOrchestrator extends ChangeNotifier {
       preambles.add(_teamSystemPrompt(name, spec.role));
     }
     final bootstrap = agentBootstrap(spec.cwd, base: spec.env);
-    sessionArgs = ['--append-system-prompt', preambles.join('\n\n'), ...bootstrap.extraArgs, ...sessionArgs];
+    sessionArgs = [
+      '--append-system-prompt',
+      preambles.join('\n\n'),
+      ...bootstrap.extraArgs,
+      if (spec.effort != null) ...['--effort', spec.effort!],
+      ...sessionArgs,
+    ];
 
     final proc = await _factory(sessionArgs: sessionArgs, cwd: spec.cwd, env: bootstrap.envDelta);
     final session = StreamJsonSession(proc, mcpServers: mcpServers)..start();