fix: resolve all 41 pre-existing dashboard test failures

- AgentsView: add missing fetchModels/fetchAgentStats mocks, update tests
  for new multi-step NewAgentDialog and ActiveAgentsPanel dual rendering
- routes-diff: rewrite tests to match new resolveDiffBase() two-dot syntax
- routes.test: fix spec/revise test — done→triage is valid per VALID_TRANSITIONS
- activity-feed CSS: replace hardcoded rgba(88,166,255) with color-mix token,
  fix var(--error) → var(--color-error)
- server/webhook/websocket tests: add getDatabase() mock for AiSessionStore

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

packages/dashboard/src/__tests__/websocket.test.ts

@@ -48,6 +48,13 @@ class MockStore extends EventEmitter {
     return process.cwd();
   }
 
+  getDatabase() {
+    return {
+      exec: vi.fn(),
+      prepare: vi.fn().mockReturnValue({ run: vi.fn().mockReturnValue({ changes: 0 }), get: vi.fn(), all: vi.fn().mockReturnValue([]) }),
+    };
+  }
+
   async listTasks(): Promise<Task[]> {
     return [this.task];
   }