hermes(router-plugin): deliver hux_mode.py through the auto-router ConfigMap

The generator now ships the HUX-06 adoption module alongside the
plugin, and the plugin degrades to its previous behaviour (no mode
adoption) if it starts against a ConfigMap rendered before the module
existed - the plugin can never fail to load mid-transition.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01BvMSXH8VH2tMWXanb8SJdf

services/hermes/kustomization.yaml

@@ -188,6 +188,7 @@ configMapGenerator:
     namespace: hermes
     files:
       - __init__.py=plugins/auto-router/__init__.py
+      - hux_mode.py=plugins/auto-router/hux_mode.py
       - provider_status.py=plugins/auto-router/provider_status.py
       - plugin.yaml=plugins/auto-router/plugin.yaml
       - dashboard-manifest.json=plugins/auto-router/dashboard/manifest.json

services/hermes/plugins/auto-router/__init__.py

@@ -15,8 +15,12 @@ except ImportError:  # Direct module loading in the small unit-test harness.
 
 try:
     from .hux_mode import selection as _hux_mode_selection
-except ImportError:  # Direct module loading in the small unit-test harness.
-    from hux_mode import selection as _hux_mode_selection
+except ImportError:
+    try:  # Direct module loading in the small unit-test harness.
+        from hux_mode import selection as _hux_mode_selection
+    except ImportError:  # A ConfigMap rendered before hux_mode.py shipped.
+        def _hux_mode_selection(session):  # noqa: ARG001 - contract shim
+            return None
 
 
 POLICY_PATH = Path("/opt/data/workspace/coordinator/route-policy.json")