fix(tools): guard Path.home() against PermissionError in has_direct_modal_credentials (#33528)

When HOME=/root (Docker containers) and the process runs as unprivileged
user (hermes, uid 10000), Path.home() / '.modal.toml' raises PermissionError
because /root/ is inaccessible. This crashes the dashboard /api/skills endpoint.

Catch PermissionError/OSError and treat as 'no config file'. Env vars still
take priority (tested).

Fixes #33525

tests/tools/test_tool_backend_helpers.py

@@ -242,6 +242,20 @@ class TestHasDirectModalCredentials:
         with patch.object(Path, "home", return_value=tmp_path):
             assert has_direct_modal_credentials() is True
 
+    def test_home_dir_permission_denied(self, monkeypatch):
+        """PermissionError on Path.home() should not crash (issue #33525)."""
+        monkeypatch.delenv("MODAL_TOKEN_ID", raising=False)
+        monkeypatch.delenv("MODAL_TOKEN_SECRET", raising=False)
+        with patch.object(Path, "home", side_effect=PermissionError("denied")):
+            assert has_direct_modal_credentials() is False
+
+    def test_home_dir_permission_denied_with_env_vars(self, monkeypatch):
+        """PermissionError on Path.home() should not prevent env var detection."""
+        monkeypatch.setenv("MODAL_TOKEN_ID", "id-123")
+        monkeypatch.setenv("MODAL_TOKEN_SECRET", "sec-456")
+        with patch.object(Path, "home", side_effect=PermissionError("denied")):
+            assert has_direct_modal_credentials() is True
+
 
 # ---------------------------------------------------------------------------
 # prefers_gateway