fix: route parent-directory creation through the JSON write try/except

Was leaking unhandled OSError tracebacks when the output's parent
path could not be created. Exit code stays 1; user-facing message
matches the existing write-failure path.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

tools/pz-analyzer/pz_classify.py

@@ -247,9 +247,9 @@ def _run(input_dir: Path, out_path: Path, *, quiet: bool) -> int:
         "summary": _build_summary(merged),
     }
 
-    out_path.parent.mkdir(parents=True, exist_ok=True)
     tmp = out_path.with_suffix(out_path.suffix + ".tmp")
     try:
+        out_path.parent.mkdir(parents=True, exist_ok=True)
         with tmp.open("w", encoding="utf-8") as f:
             json.dump(document, f, ensure_ascii=False, indent=2)
             f.write("\n")