feat(engine): add background project engine reconciliation + global concurrency setting

- ProjectEngineManager.startReconciliation() polls for newly registered
  projects every 30s and starts their engines without requiring UI access
- Expose global concurrency limit in dashboard settings
- Fix SettingsModal test cleanup

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

packages/dashboard/app/components/__tests__/SettingsModal.test.tsx

@@ -38,8 +38,6 @@ vi.mock("../../api", () => ({
   fetchSettings: vi.fn(() => Promise.resolve({ ...defaultSettings })),
   updateSettings: vi.fn(() => Promise.resolve({ ...defaultSettings })),
   updateGlobalSettings: vi.fn(() => Promise.resolve({ ...defaultSettings })),
-  fetchGlobalConcurrency: vi.fn(() => Promise.resolve({ globalMaxConcurrent: 4, currentlyActive: 0, queuedCount: 0, projectsActive: {} })),
-  updateGlobalConcurrency: vi.fn(() => Promise.resolve({ globalMaxConcurrent: 4, currentlyActive: 0, queuedCount: 0, projectsActive: {} })),
   fetchAuthStatus: vi.fn(() => Promise.resolve({ providers: [{ id: "anthropic", name: "Anthropic", authenticated: false }] })),
   loginProvider: vi.fn(() => Promise.resolve({ url: "https://auth.example.com/login" })),
   logoutProvider: vi.fn(() => Promise.resolve({ success: true })),
@@ -66,8 +64,6 @@ vi.mock("../../api", () => ({
   fetchPluginSettings: vi.fn(() => Promise.resolve({})),
   updatePluginSettings: vi.fn(() => Promise.resolve({})),
   reloadPlugin: vi.fn(() => Promise.resolve({ id: "test-plugin", name: "Test Plugin", version: "1.0.0", state: "started" as const, enabled: true, settings: {}, settingsSchema: {} })),
-  fetchGlobalConcurrency: vi.fn(() => Promise.resolve({ globalMaxConcurrent: 4, currentlyActive: 0, queuedCount: 0, projectsActive: {} })),
-  updateGlobalConcurrency: vi.fn(() => Promise.resolve({ globalMaxConcurrent: 4, currentlyActive: 0, queuedCount: 0, projectsActive: {} })),
   fetchBackups: vi.fn(() => Promise.resolve({ backups: [], totalSize: 0 })),
   createBackup: vi.fn(() => Promise.resolve({ success: true })),
   exportSettings: vi.fn(() => Promise.resolve({ version: 1, exportedAt: new Date().toISOString(), global: undefined, project: {} })),

packages/dashboard/app/components/__tests__/settings-mobile.test.tsx

@@ -37,7 +37,6 @@ vi.mock("../../api", () => ({
   fetchSettings: vi.fn(() => Promise.resolve({ ...defaultSettings })),
   updateSettings: vi.fn(() => Promise.resolve({ ...defaultSettings })),
   updateGlobalSettings: vi.fn(() => Promise.resolve({ ...defaultSettings })),
-  fetchGlobalConcurrency: vi.fn(() => Promise.resolve({ globalMaxConcurrent: 4, currentlyActive: 0, queuedCount: 0, projectsActive: {} })),
   fetchAuthStatus: vi.fn(() => Promise.resolve({ providers: [{ id: "anthropic", name: "Anthropic", authenticated: false }] })),
   loginProvider: vi.fn(() => Promise.resolve({ url: "https://auth.example.com/login" })),
   logoutProvider: vi.fn(() => Promise.resolve({ success: true })),

packages/dashboard/src/server.ts

@@ -145,8 +145,14 @@ export interface ServerOptions {
   chatManager?: import("./chat.js").ChatManager;
   /**
    * Called once when a secondary project (identified by projectId query param)
-   * is first accessed via a project-scoped API or SSE request. Use this to
-   * lazily start an engine for that project.
+   * is first accessed via a project-scoped API or SSE request.
+   *
+   * @deprecated This callback is a fast-path fallback for immediate engine
+   * startup on project access. ProjectEngineManager.startReconciliation() is
+   * the primary mechanism for ensuring all registered projects have engines
+   * started — it runs without requiring any UI or API access. This callback
+   * is NOT required for correctness; it only provides a potential optimization
+   * for projects that are accessed before the next reconciliation tick.
    */
   onProjectFirstAccessed?: (projectId: string) => void;
 }