refactor(update): inline the tests exclusion; fix comments the wider purge made stale

`_STALE_PURGE_EXCLUDED_TOP_LEVEL` had one reader and a re-export nothing patched;
the config-check comment claimed root modules stay cached across the purge (no
longer true); the purge test module docstring still described package prefixes.

hermes_cli/update_cmd.py

@@ -98,7 +98,7 @@ from hermes_cli.update_cmd_git import (  # noqa: F401
     _sync_with_upstream_if_needed)
 from hermes_cli.update_cmd_maint import (  # noqa: F401
     _PRE_UPDATE_SNAPSHOT_KEEP, _PRE_UPDATE_SNAPSHOT_MAX_FILE_SIZE,
-    _STALE_PURGE_EXCLUDED_TOP_LEVEL, _STALE_PURGE_PROTECTED,
+    _STALE_PURGE_PROTECTED,
     _UPDATE_RUNTIME_RELOAD_MODULES, _clear_stale_sqlite_sidecars,
     _ensure_acp_launcher, _ensure_fhs_path_guard, _finish_dashboard_update_cleanup,
     _format_time_ago, _post_update_sqlite_runtime_status, _print_bundled_skills_sync_report,

hermes_cli/update_cmd_config.py

@@ -186,8 +186,8 @@ def _check_and_apply_config_migration(
         _m()._purge_stale_hermes_modules()
         # Reload BEFORE any config reads so all checks use the updated code.
         _reload_config_modules()
-        # Post-purge this re-executes the NEW config.py against whatever root modules
-        # (hermes_constants, utils, ...) are still cached, so it can fail too.
+        # Post-purge this re-executes the NEW config.py; it still fails if the pulled tree
+        # is internally inconsistent, hence the try.
         from hermes_cli.config import get_missing_env_vars, get_missing_config_fields
         # Log, point at the manual command, and return. See #91360.
         missing_env = get_missing_env_vars(required_only=True)

hermes_cli/update_cmd_maint.py

@@ -25,10 +25,6 @@ logger = logging.getLogger("hermes_cli.update_cmd")
 
 _UPDATE_RUNTIME_RELOAD_MODULES = "hermes_constants", "tools.environments.local", "tools.lazy_deps"
 
-#: Owned by the checkout but never purged: pytest resolves fixtures through the identity of
-#: its own already-imported test modules, and evicting them mid-session breaks that.
-_STALE_PURGE_EXCLUDED_TOP_LEVEL = frozenset({"tests"})
-
 #: Modules EXECUTING the update survive the purge: evicting them buys nothing (running frames
 #: keep them alive) and reloading them mid-flight is the one genuinely unsafe move.
 #: ``hermes_logging`` is protected for a different reason: its queue listener, handler list and
@@ -105,7 +101,9 @@ def _stale_purge_prefixes() -> frozenset:
             names.add(entry.stem)
         elif (entry / "__init__.py").is_file():
             names.add(entry.name)
-    return frozenset(names) - _STALE_PURGE_EXCLUDED_TOP_LEVEL
+    # ``tests`` is owned by the checkout but never purged: the in-process purge tests would
+    # otherwise re-import a fresh copy of the very test module their monkeypatches point at.
+    return frozenset(names) - {"tests"}
 
 
 def _purge_stale_hermes_modules() -> None:

tests/hermes_cli/test_update_stale_module_purge.py

@@ -9,9 +9,10 @@ import ...` in the restart phase raised ImportError, the whole phase
 aborted, and the running gateway kept serving pre-update code.
 
 The old mitigation (_UPDATE_RUNTIME_RELOAD_MODULES) reloaded 3 hardcoded
-modules — re-fixed per symptom. The purge evicts EVERY cached module under
-the Hermes package prefixes so later imports rebuild a self-consistent
-module graph from the updated checkout.
+modules — re-fixed per symptom. The purge evicts EVERY cached module whose
+top-level name is a ``.py`` file or package in the checkout root (minus
+``tests``) so later imports rebuild a self-consistent module graph from the
+updated checkout.
 """
 
 from __future__ import annotations