fix(file_tools): block /private/etc writes on macOS symlink bypass

On macOS, /etc is a symlink to /private/etc, so os.path.realpath()
resolves /etc/hosts to /private/etc/hosts. The sensitive path check
only matched /etc/ prefixes against the resolved path, allowing
writes to system files on macOS.

- Add /private/etc/ and /private/var/ to _SENSITIVE_PATH_PREFIXES
- Check both realpath-resolved and normpath-normalized paths
- Add regression tests for macOS symlink bypass

Closes #8734
Co-authored-by: ElhamDevelopmentStudio (PR #8829)

tests/tools/test_file_write_safety.py

@@ -79,5 +79,33 @@ class TestSafeWriteRoot:
         assert _is_write_denied(os.path.expanduser("~/.ssh/id_rsa")) is True
 
 
+class TestCheckSensitivePathMacOSBypass:
+    """Verify _check_sensitive_path blocks /private/etc paths (issue #8734)."""
+
+    def test_etc_hosts_blocked(self):
+        from tools.file_tools import _check_sensitive_path
+        assert _check_sensitive_path("/etc/hosts") is not None
+
+    def test_private_etc_hosts_blocked(self):
+        from tools.file_tools import _check_sensitive_path
+        assert _check_sensitive_path("/private/etc/hosts") is not None
+
+    def test_private_etc_ssh_config_blocked(self):
+        from tools.file_tools import _check_sensitive_path
+        assert _check_sensitive_path("/private/etc/ssh/sshd_config") is not None
+
+    def test_private_var_blocked(self):
+        from tools.file_tools import _check_sensitive_path
+        assert _check_sensitive_path("/private/var/db/something") is not None
+
+    def test_boot_still_blocked(self):
+        from tools.file_tools import _check_sensitive_path
+        assert _check_sensitive_path("/boot/grub/grub.cfg") is not None
+
+    def test_safe_path_allowed(self):
+        from tools.file_tools import _check_sensitive_path
+        assert _check_sensitive_path("/tmp/safe_file.txt") is None
+
+
 if __name__ == "__main__":
     pytest.main([__file__, "-v"])