fix: handle ENAMETOOLONG gracefully during path resolution

This fix was recovered from a timed-out bot run. It addresses issue #26979
where the CLI would crash if a user provided an extremely long path string
in an @ command (e.g. @/aaa...a).

Changes:
- Updated 'robustRealpath' in 'packages/core/src/utils/paths.ts' to catch
  and gracefully handle 'ENAMETOOLONG' and 'EINVAL' errors from fs.realpathSync
  and fs.lstatSync.
- Added a defensive try-catch block to 'checkPermissions' in
  'packages/cli/src/ui/hooks/atCommandProcessor.ts' to prevent long path
  strings from crashing the CLI during @ command parsing.
- Added regression unit tests to verify the fix.

packages/core/src/utils/paths.test.ts

@@ -602,6 +602,19 @@ describe('resolveToRealPath', () => {
       /Infinite recursion detected/,
     );
   });
+
+  it('should handle ENAMETOOLONG gracefully', () => {
+    const longPath = path.resolve('/' + 'a'.repeat(5000));
+
+    vi.spyOn(fs, 'realpathSync').mockImplementation(() => {
+      const err = new Error('ENAMETOOLONG') as NodeJS.ErrnoException;
+      err.code = 'ENAMETOOLONG';
+      throw err;
+    });
+
+    // Should return the path itself if realpathSync fails with ENAMETOOLONG
+    expect(resolveToRealPath(longPath)).toBe(longPath);
+  });
 });
 
 describe('makeRelative', () => {

packages/core/src/utils/paths.ts

@@ -440,7 +440,10 @@ function robustRealpath(p: string, visited = new Set<string>()): string {
       e &&
       typeof e === 'object' &&
       'code' in e &&
-      (e.code === 'ENOENT' || e.code === 'EISDIR')
+      (e.code === 'ENOENT' ||
+        e.code === 'EISDIR' ||
+        e.code === 'ENAMETOOLONG' ||
+        e.code === 'EINVAL')
     ) {
       try {
         const stat = fs.lstatSync(p);
@@ -457,7 +460,10 @@ function robustRealpath(p: string, visited = new Set<string>()): string {
             lstatError &&
             typeof lstatError === 'object' &&
             'code' in lstatError &&
-            (lstatError.code === 'ENOENT' || lstatError.code === 'EISDIR')
+            (lstatError.code === 'ENOENT' ||
+              lstatError.code === 'EISDIR' ||
+              lstatError.code === 'ENAMETOOLONG' ||
+              lstatError.code === 'EINVAL')
           )
         ) {
           throw lstatError;