Chore: enable pylint warning (PLW) ruff rules

Full category (not just the ruff-0.16 default subset). 35 hits:
- 4 PLW0108 (unnecessary lambda) autofixed
- 6 PLW2901 (loop/with variable shadowed) renamed to distinct names
- 2 PLW1510 (subprocess.run without explicit check) given check=False,
  matching existing behavior exactly
- 6 PLW0602 (global declared but never assigned) removed - these were
  all in-place mutations (.append/.insert), not reassignments, so
  `global` was already a no-op
- 7 PLW0603 (global statement) suppressed with noqa - these are
  genuine lazy-init singletons with no class to hold the state;
  refactoring them is a separate, larger change
- 6 PLW1508 (non-str/None env var default) fixed using the existing
  get_int_from_env/get_float_from_env typed helpers instead of raw
  os.getenv, which also fixes a real bug: LOGROTATE_MAX_SIZE and
  LOGROTATE_MAX_BACKUPS were never wrapped in int(), so a string env
  var value would have flowed into RotatingFileHandler as a string
- 1 PLW1641 (__eq__ without __hash__) fixed by adding __hash__ to
  PlaceholderString

src/documents/tasks.py

@@ -217,9 +217,9 @@ def consume_file(
                 overrides.filename or input_doc.original_file.name,
                 self.request.id,
             ) as status_mgr,
-            TemporaryDirectory(dir=settings.SCRATCH_DIR) as tmp_dir,
+            TemporaryDirectory(dir=settings.SCRATCH_DIR) as tmp_dir_name,
         ):
-            tmp_dir = Path(tmp_dir)
+            tmp_dir = Path(tmp_dir_name)
             msg = None
             for plugin_class in plugins:
                 plugin_name = plugin_class.NAME