fix: disable gpg signing in test git fixtures and skip root-only permission test

Test fixtures that create temporary git repos now set commit.gpgsign=false
to avoid failures in environments with global commit signing configured.
The permission error test is skipped when running as root since file
permissions don't apply to the root user.

https://claude.ai/code/session_018u1fAx2GihSGctYS64tD4H

tests/self_coding/test_codebase_indexer_errors.py

@@ -273,31 +273,34 @@ except ImportError:
     
     async def test_permission_error(self):
         """Should handle permission errors gracefully."""
+        import os
+        if os.geteuid() == 0:
+            pytest.skip("Permission tests are ineffective when running as root")
+
         with tempfile.TemporaryDirectory() as tmpdir:
             repo_path = Path(tmpdir)
             src_path = repo_path / "src"
             src_path.mkdir()
-            
+
             # Create file
             file_path = src_path / "locked.py"
             file_path.write_text("def test(): pass")
-            
+
             # Remove read permission (if on Unix)
-            import os
             try:
                 os.chmod(file_path, 0o000)
-                
+
                 indexer = CodebaseIndexer(
                     repo_path=repo_path,
                     db_path=repo_path / "index.db",
                     src_dirs=["src"],
                 )
-                
+
                 stats = await indexer.index_all()
-                
+
                 # Should count as failed
                 assert stats["failed"] == 1
-                
+
             finally:
                 # Restore permission for cleanup
                 os.chmod(file_path, 0o644)