fix(scripts): resolve worktree root before relative_to in type_check_gate (#31906)

On macOS, tempfile.mkdtemp returns a path under /var/folders, a symlink
to /private/var. The base pass in type_check_gate.py resolved each
diagnostic path (yielding /private/var/...) but not the worktree root,
so relative_to raised ValueError for every diagnostic, base counts came
back empty, and the vacuous-run guard failed every local
make lint-basedpyright run. type_discipline_gate.py already resolves
root the same way; ruff_strict_gate.py counts rule codes without
touching worktree paths, so it is unaffected. CI runs Linux where the
temp dir is not a symlink, which is why this only bit local macOS runs

scripts/type_check_gate.py

@@ -63,7 +63,7 @@ def _to_relative(raw: str, root: Path) -> str | None:
     path = Path(raw)
     absolute = path if path.is_absolute() else root / path
     try:
-        return absolute.resolve().relative_to(root).as_posix()
+        return absolute.resolve().relative_to(root.resolve()).as_posix()
     except ValueError:
         return None
 

tests/test_litellm/test_type_check_gate.py

@@ -54,6 +54,21 @@ def test_paths_outside_repo_are_skipped():
     assert gate.count_basedpyright(payload) == {}
 
 
+def test_symlinked_root_keeps_diagnostics_in_tree(tmp_path):
+    real = tmp_path / "real"
+    real.mkdir()
+    link = tmp_path / "link"
+    link.symlink_to(real)
+    payload = json.dumps(
+        {
+            "generalDiagnostics": [
+                _bpr(link / "litellm" / "x.py", "error", "reportArgumentType")
+            ]
+        }
+    )
+    assert gate.count_basedpyright(payload, root=link) == {"reportArgumentType": 1}
+
+
 def test_at_or_under_ceiling_passes():
     budget = {"no-any-return": {"limit": 5}}
     assert gate.evaluate({"no-any-return": 5}, {}, budget) == []