fix(dashboard): lazy-init useMobileKeyboard so remount has no stale render

When ChatView remounted (e.g. tab switch with keyboard still up), the
hook started with keyboardOpen=false and corrected itself only after
the effect ran. That single stale-state render briefly unhid the
executor status bar, which appeared as a blank pane covering half the
input box before the next state update settled it.

useState initializers now call getKeyboardMetrics() lazily on first
render so the very first paint already reflects the live keyboard
state.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

packages/engine/src/__tests__/pi.test.ts

@@ -662,11 +662,53 @@ describe("session failure diagnostics", () => {
     await expect((session as any).promptWithFallback("Run task")).resolves.toBeUndefined();
 
     expect(warnSpy).toHaveBeenCalledWith(
-      expect.stringContaining("Failed to dispose session during model fallback swap: dispose failed"),
+      expect.stringContaining("Failed to dispose session during swap: dispose failed"),
     );
 
     warnSpy.mockRestore();
   });
+
+  it("retries prompt on thinking/reasoning conflict without switching fallback models", async () => {
+    const createAgentSessionMock = vi.mocked(createAgentSession);
+
+    const firstSession = {
+      model: { provider: "test", id: "primary-model" },
+      prompt: vi.fn().mockRejectedValue(new Error("400 cannot specify both 'thinking' and 'reasoning_effort'")),
+      subscribe: vi.fn(),
+      dispose: vi.fn(),
+      setThinkingLevel: vi.fn(),
+      sessionFile: undefined,
+    } as unknown as AgentSession;
+
+    const retrySession = {
+      model: { provider: "test", id: "primary-model" },
+      prompt: vi.fn().mockResolvedValue(undefined),
+      subscribe: vi.fn(),
+      dispose: vi.fn(),
+      setThinkingLevel: vi.fn(),
+      sessionFile: undefined,
+    } as unknown as AgentSession;
+
+    createAgentSessionMock.mockReset();
+    createAgentSessionMock
+      .mockResolvedValueOnce({ session: firstSession } as any)
+      .mockResolvedValueOnce({ session: retrySession } as any);
+
+    const { session } = await createFnAgent({
+      cwd: "/test/project",
+      systemPrompt: "Test thinking compatibility",
+      defaultProvider: "test",
+      defaultModelId: "primary-model",
+      fallbackProvider: "test",
+      fallbackModelId: "fallback-model",
+      defaultThinkingLevel: "high",
+    });
+
+    await expect((session as any).promptWithFallback("Run review")).resolves.toBeUndefined();
+
+    expect(createAgentSessionMock).toHaveBeenCalledTimes(2);
+    expect((retrySession.setThinkingLevel as any).mock.calls.length).toBe(0);
+  });
 });
 
 describe("piLog structured diagnostics", () => {