feat: add runtime provider/model switching via /model <tier> <provider/model>

- ModelRouter: add setClient(), labels map, getLabel(), getAllLabels()
- TUI commands: parse /model <tier> <provider/model> syntax with autocompletion
- TUI minimal: handle provider switching via createClientFromConfig factory
- Daemon: wire initial labels into router config
- Fix /model alias mappings (opus=complex, sonnet=default, haiku=fast)
- Add design doc and update state.json with feature status

src/models/router.test.ts

@@ -169,3 +169,149 @@ describe('ModelRouter local client switching', () => {
     expect(router.getClient('local')).toBe(mockLocal2);
   });
 });
+
+describe('setClient and labels', () => {
+  it('setClient replaces an existing tier client', async () => {
+    const mockClient1 = { chat: vi.fn() } as unknown as ModelClient;
+    const mockClient2 = { chat: vi.fn() } as unknown as ModelClient;
+
+    const router = new ModelRouter({
+      default: { chat: vi.fn() } as unknown as ModelClient,
+      fast: mockClient1,
+      fallbackChain: [],
+    });
+
+    await router.chat({ messages: [{ role: 'user', content: 'Test' }] }, 'fast');
+
+    expect(mockClient1.chat).toHaveBeenCalled();
+    expect(mockClient1.chat).toHaveBeenCalledTimes(1);
+
+    router.setClient('fast', mockClient2, 'fast-replaced');
+
+    const newFastClient = router.getClient('fast');
+    expect(newFastClient).toBeDefined();
+    await router.chat({ messages: [{ role: 'user', content: 'Test' }] }, 'fast');
+
+    expect(newFastClient!.chat).toHaveBeenCalled();
+    expect(newFastClient!.chat).toHaveBeenCalledTimes(1);
+    expect(mockClient1.chat).toHaveBeenCalledTimes(1);
+  });
+
+  it('setClient adds a new tier client', async () => {
+    const mockClient1 = { chat: vi.fn() } as unknown as ModelClient;
+    const mockClient2 = { chat: vi.fn() } as unknown as ModelClient;
+
+    const router = new ModelRouter({
+      default: mockClient1,
+      fallbackChain: [],
+    });
+
+    expect(router.getClient('complex')).toBeUndefined();
+
+    router.setClient('complex', mockClient2, 'complex-tier');
+
+    const newClient = router.getClient('complex');
+    expect(newClient).toBe(mockClient2);
+
+    await router.chat({ messages: [{ role: 'user', content: 'Test' }] }, 'complex');
+
+    expect(newClient!.chat).toHaveBeenCalled();
+  });
+
+  it('getLabel returns the label set by setClient', () => {
+    const router = new ModelRouter({
+      default: { chat: vi.fn() } as unknown as ModelClient,
+      fallbackChain: [],
+    });
+
+    expect(router.getLabel('fast')).toBe('unknown');
+
+    router.setClient('fast', { chat: vi.fn() } as unknown as ModelClient, 'fast-tier');
+
+    expect(router.getLabel('fast')).toBe('fast-tier');
+  });
+
+  it('getLabel returns "unknown" for unset tier', () => {
+    const router = new ModelRouter({
+      default: { chat: vi.fn() } as unknown as ModelClient,
+      fallbackChain: [],
+    });
+
+    expect(router.getLabel('fast')).toBe('unknown');
+    expect(router.getLabel('complex')).toBe('unknown');
+  });
+
+  it('getAllLabels returns all tier labels', () => {
+    const router = new ModelRouter({
+      default: { chat: vi.fn() } as unknown as ModelClient,
+      fallbackChain: [],
+    });
+
+    const labels = router.getAllLabels();
+    expect(labels).toEqual({});
+
+    router.setClient('fast', { chat: vi.fn() } as unknown as ModelClient, 'fast-tier');
+    router.setClient('complex', { chat: vi.fn() } as unknown as ModelClient, 'complex-tier');
+
+    const allLabels = router.getAllLabels();
+    expect(allLabels).toEqual({
+      fast: 'fast-tier',
+      complex: 'complex-tier',
+    });
+  });
+
+  it('constructor accepts initial labels', async () => {
+    const mockClient1 = { chat: vi.fn() } as unknown as ModelClient;
+    const mockClient2 = { chat: vi.fn() } as unknown as ModelClient;
+
+    const router = new ModelRouter({
+      default: mockClient1,
+      fast: mockClient2,
+      fallbackChain: [],
+      labels: {
+        default: 'default-tier',
+        fast: 'fast-tier',
+      },
+    });
+
+    expect(router.getClient('default')).toBe(mockClient1);
+    expect(router.getClient('fast')).toBe(mockClient2);
+    expect(router.getLabel('default')).toBe('default-tier');
+    expect(router.getLabel('fast')).toBe('fast-tier');
+    expect(router.getLabel('complex')).toBe('unknown');
+
+    await router.chat({ messages: [{ role: 'user', content: 'Hi' }] }, 'fast');
+
+    expect(mockClient2.chat).toHaveBeenCalled();
+  });
+
+  it('chat uses the new client after setClient', async () => {
+    const mockClient1 = { chat: vi.fn() } as unknown as ModelClient;
+    const mockClient2 = { chat: vi.fn() } as unknown as ModelClient;
+
+    const router = new ModelRouter({
+      default: mockClient1,
+      fast: { chat: vi.fn() } as unknown as ModelClient,
+      fallbackChain: [],
+      labels: {
+        fast: 'original-fast',
+      },
+    });
+
+    const initialFastClient = router.getClient('fast');
+    expect(initialFastClient).toBeDefined();
+    await router.chat({ messages: [{ role: 'user', content: 'Test' }] }, 'fast');
+
+    expect(initialFastClient!.chat).toHaveBeenCalled();
+    expect(initialFastClient!.chat).toHaveBeenCalledTimes(1);
+
+    router.setClient('fast', mockClient2, 'fast-replaced');
+
+    const newFastClient = router.getClient('fast');
+    await router.chat({ messages: [{ role: 'user', content: 'Test' }] }, 'fast');
+
+    expect(newFastClient!.chat).toHaveBeenCalled();
+    expect(newFastClient!.chat).toHaveBeenCalledTimes(1);
+    expect(initialFastClient!.chat).toHaveBeenCalledTimes(1);
+  });
+});