refactor(tools): lift engine ensure/sub-section boilerplate into _Engine.__init__/_build, contextlib.suppress for swallow-only try/except, collapse yuanbao _err into _YbError, fold pending-dir helpers

tools/working_diff.py

@@ -12,6 +12,7 @@ from __future__ import annotations
 import os
 import shutil
 import subprocess
+from contextlib import suppress
 from typing import Dict, List
 
 from hermes_cli._subprocess_compat import harden_git_argv, noninteractive_git_env
@@ -49,13 +50,11 @@ def _untracked_diff(cwd: str, files: List[str]) -> str:
     """Render untracked files as new-file diffs via ``git diff --no-index``."""
     chunks: List[str] = []
     for rel in files[:_MAX_UNTRACKED_FILES]:
-        try:
+        with suppress(subprocess.TimeoutExpired, OSError):
             # --no-index exits 1 when files differ — the success path, so the code is ignored.
             _, out = _run(["diff", "--no-index", "--", os.devnull, rel], cwd)
             if out.strip():
                 chunks.append(out.rstrip("\n"))
-        except (subprocess.TimeoutExpired, OSError):
-            continue
     if len(files) > _MAX_UNTRACKED_FILES:
         chunks.append(f"... ({len(files) - _MAX_UNTRACKED_FILES} more untracked files not shown)")
     return "\n".join(chunks)