test: add shared mock infrastructure and route tests (phase 7)

Consolidate duplicated MockSession/MockStateStore into test/mocks/,
migrate respawn tests to shared mocks, and add 58 route tests for
session, system, and respawn endpoints using Fastify app.inject().

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

test/mocks/mock-state-store.ts

@@ -0,0 +1,60 @@
+/**
+ * Shared MockStateStore for tests.
+ *
+ * Includes methods for both session management and Ralph loop testing.
+ * All methods are vi.fn() spies — tests can override return values as needed.
+ *
+ * NOTE: This is for direct instantiation in new tests. Existing tests that
+ * use vi.mock('../src/state-store.js') keep their inline definitions.
+ */
+import { vi } from 'vitest';
+
+export class MockStateStore {
+  state: Record<string, unknown> = {
+    sessions: {} as Record<string, unknown>,
+    config: { maxConcurrentSessions: 5 },
+    ralphLoop: { status: 'stopped' },
+    tasks: {} as Record<string, unknown>,
+  };
+
+  // Session methods
+  getConfig = vi.fn(() => this.state.config);
+  getSessions = vi.fn(() => this.state.sessions as Record<string, unknown>);
+  getSession = vi.fn((id: string) => (this.state.sessions as Record<string, unknown>)[id]);
+  setSession = vi.fn((id: string, state: unknown) => {
+    (this.state.sessions as Record<string, unknown>)[id] = state;
+  });
+  removeSession = vi.fn((id: string) => {
+    delete (this.state.sessions as Record<string, unknown>)[id];
+  });
+
+  // Ralph state methods
+  getRalphLoopState = vi.fn(() => this.state.ralphLoop);
+  setRalphLoopState = vi.fn((update: Record<string, unknown>) => {
+    this.state.ralphLoop = { ...(this.state.ralphLoop as Record<string, unknown>), ...update };
+  });
+
+  // Task methods
+  getTasks = vi.fn(() => this.state.tasks);
+  setTask = vi.fn();
+  removeTask = vi.fn();
+
+  // Settings methods
+  getSettings = vi.fn(() => ({}));
+  setSettings = vi.fn();
+
+  // Generic persistence
+  save = vi.fn();
+  load = vi.fn();
+
+  /** Reset all state and mocks for clean test isolation */
+  reset(): void {
+    this.state = {
+      sessions: {},
+      config: { maxConcurrentSessions: 5 },
+      ralphLoop: { status: 'stopped' },
+      tasks: {},
+    };
+    vi.clearAllMocks();
+  }
+}