fix(windows): align escaped wrapper shell handling

Use ComSpec-aware shell selection for escaped wrapper launches.

Apply it to the remaining Windows Claude launch paths.

Rewrite the Codex exec regression test to use scoped spies so the full suite stays isolated.

tests/unit/utils/shell-executor.test.ts

@@ -81,6 +81,56 @@ describe('escapeShellArg', () => {
       const { escapeShellArg } = await import('../../../src/utils/shell-executor');
       expect(escapeShellArg('hello!')).toBe('"hello^^!"');
     });
+
+    it('prefers ComSpec when resolving the escaped command shell', async () => {
+      const originalComSpec = process.env.ComSpec;
+      const originalCOMSPEC = process.env.COMSPEC;
+
+      try {
+        process.env.ComSpec = 'C:\\Windows\\System32\\cmd.exe';
+        delete process.env.COMSPEC;
+        const { getWindowsEscapedCommandShell } = await import(
+          '../../../src/utils/shell-executor'
+        );
+        expect(getWindowsEscapedCommandShell()).toBe('C:\\Windows\\System32\\cmd.exe');
+      } finally {
+        if (originalComSpec === undefined) delete process.env.ComSpec;
+        else process.env.ComSpec = originalComSpec;
+        if (originalCOMSPEC === undefined) delete process.env.COMSPEC;
+        else process.env.COMSPEC = originalCOMSPEC;
+      }
+    });
+
+    it('falls back to cmd.exe when ComSpec is unavailable', async () => {
+      const originalComSpec = process.env.ComSpec;
+      const originalCOMSPEC = process.env.COMSPEC;
+
+      try {
+        delete process.env.ComSpec;
+        delete process.env.COMSPEC;
+        const { getWindowsEscapedCommandShell } = await import(
+          '../../../src/utils/shell-executor'
+        );
+        expect(getWindowsEscapedCommandShell()).toBe('cmd.exe');
+      } finally {
+        if (originalComSpec === undefined) delete process.env.ComSpec;
+        else process.env.ComSpec = originalComSpec;
+        if (originalCOMSPEC === undefined) delete process.env.COMSPEC;
+        else process.env.COMSPEC = originalCOMSPEC;
+      }
+    });
+  });
+});
+
+describe('getWindowsEscapedCommandShell', () => {
+  afterEach(() => {
+    Object.defineProperty(process, 'platform', { value: originalPlatform });
+  });
+
+  it('returns shell=true outside Windows if called defensively', async () => {
+    Object.defineProperty(process, 'platform', { value: 'linux' });
+    const { getWindowsEscapedCommandShell } = await import('../../../src/utils/shell-executor');
+    expect(getWindowsEscapedCommandShell()).toBe(true);
   });
 });