fix(tools): harden scheduler limits and logs

Guard scheduler system actions against pending work, serialize diagnostic log transitions, and keep speed-limit saves truthful after backend failures.\n\nNo linked issue was found for this audit.

src/utils/logger.test.ts

@@ -0,0 +1,61 @@
+import { beforeEach, describe, expect, it, vi } from 'vitest';
+
+const { invoke } = vi.hoisted(() => ({ invoke: vi.fn() }));
+
+vi.mock('@tauri-apps/api/core', () => ({ invoke }));
+vi.mock('@tauri-apps/plugin-log', () => ({
+  attachLogger: vi.fn(),
+  debug: vi.fn(),
+  error: vi.fn(),
+  info: vi.fn(),
+  trace: vi.fn(),
+  warn: vi.fn()
+}));
+
+import { setLogPaused, setLogStreamActive } from './logger';
+
+describe('logger stream transitions', () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+  });
+
+  it('serializes enable and disable transitions', async () => {
+    let releaseFirst!: () => void;
+    invoke
+      .mockImplementationOnce(() => new Promise<void>(resolve => { releaseFirst = resolve; }))
+      .mockResolvedValueOnce(undefined);
+
+    const enabling = setLogStreamActive(true);
+    const disabling = setLogStreamActive(false);
+    await Promise.resolve();
+
+    expect(invoke).toHaveBeenCalledTimes(1);
+    releaseFirst();
+    await Promise.all([enabling, disabling]);
+
+    expect(invoke.mock.calls).toEqual([
+      ['set_log_stream_active', { active: true }],
+      ['set_log_stream_active', { active: false }]
+    ]);
+  });
+
+  it('serializes pause transitions so the backend cannot finish out of order', async () => {
+    let releaseFirst!: () => void;
+    invoke
+      .mockImplementationOnce(() => new Promise<void>(resolve => { releaseFirst = resolve; }))
+      .mockResolvedValueOnce(undefined);
+
+    const pausing = setLogPaused(true);
+    const resuming = setLogPaused(false);
+    await Promise.resolve();
+
+    expect(invoke).toHaveBeenCalledTimes(1);
+    releaseFirst();
+    await Promise.all([pausing, resuming]);
+
+    expect(invoke.mock.calls).toEqual([
+      ['toggle_log_pause', { pause: true }],
+      ['toggle_log_pause', { pause: false }]
+    ]);
+  });
+});