Four small fixes:
1. model_tools.py: Tool import failures logged at WARNING instead of
DEBUG. If a tool module fails to import (syntax error, missing dep),
the user now sees a warning instead of the tool silently vanishing.
2. hermes_cli/config.py: Remove duplicate 'import sys' (lines 19, 21).
3. agent/model_metadata.py: Remove 6 duplicate entries in
DEFAULT_CONTEXT_LENGTHS dict. Python keeps the last value, so no
functional change, but removes maintenance confusion.
4. hermes_state.py: Add missing self._lock to the LIKE query in
resolve_session_id(). The exact-match path used get_session()
(which locks internally), but the prefix fallback queried _conn
without the lock.
847ee20390