fix(shell): escape ! for cmd.exe delayed expansion

Adds defensive escaping for exclamation marks in case delayed
expansion is enabled in the user's cmd.exe environment.

src/utils/shell-executor.ts

@@ -28,6 +28,7 @@ export function escapeShellArg(arg: string): string {
         .replace(/[\r\n\t]/g, ' ') // Replace newlines/tabs with space
         .replace(/%/g, '%%') // Escape percent signs
         .replace(/\^/g, '^^') // Escape carets
+        .replace(/!/g, '^^!') // Escape exclamation marks (delayed expansion)
         .replace(/"/g, '""') + // Escape quotes
       '"'
     );

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

@@ -75,5 +75,10 @@ describe('escapeShellArg', () => {
       const { escapeShellArg } = await import('../../../src/utils/shell-executor');
       expect(escapeShellArg('C:\\Program Files\\App')).toBe('"C:\\Program Files\\App"');
     });
+
+    it('escapes exclamation marks for delayed expansion', async () => {
+      const { escapeShellArg } = await import('../../../src/utils/shell-executor');
+      expect(escapeShellArg('hello!')).toBe('"hello^^!"');
+    });
   });
 });