fix: defensive hardening — logging, dedup, locks, dead code

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.

agent/model_metadata.py

@@ -94,10 +94,9 @@ DEFAULT_CONTEXT_LENGTHS = {
     "gpt-5": 128000,
     "gpt-5-codex": 128000,
     "gpt-5-nano": 128000,
-    "claude-opus-4-6": 200000,
+    # Bare model IDs without provider prefix (avoid duplicates with entries above)
     "claude-opus-4-5": 200000,
     "claude-opus-4-1": 200000,
-    "claude-sonnet-4-6": 200000,
     "claude-sonnet-4-5": 200000,
     "claude-sonnet-4": 200000,
     "claude-haiku-4-5": 200000,
@@ -108,11 +107,7 @@ DEFAULT_CONTEXT_LENGTHS = {
     "minimax-m2.5": 204800,
     "minimax-m2.5-free": 204800,
     "minimax-m2.1": 204800,
-    "glm-5": 202752,
-    "glm-4.7": 202752,
     "glm-4.6": 202752,
-    "kimi-k2.5": 262144,
-    "kimi-k2-thinking": 262144,
     "kimi-k2": 262144,
     "qwen3-coder": 32768,
     "big-pickle": 128000,

hermes_cli/config.py

@@ -16,7 +16,6 @@ import os
 import platform
 import re
 import stat
-import sys
 import subprocess
 import sys
 import tempfile

hermes_state.py

@@ -350,11 +350,12 @@ class SessionDB:
             .replace("%", "\\%")
             .replace("_", "\\_")
         )
-        cursor = self._conn.execute(
-            "SELECT id FROM sessions WHERE id LIKE ? ESCAPE '\\' ORDER BY started_at DESC LIMIT 2",
-            (f"{escaped}%",),
-        )
-        matches = [row["id"] for row in cursor.fetchall()]
+        with self._lock:
+            cursor = self._conn.execute(
+                "SELECT id FROM sessions WHERE id LIKE ? ESCAPE '\\' ORDER BY started_at DESC LIMIT 2",
+                (f"{escaped}%",),
+            )
+            matches = [row["id"] for row in cursor.fetchall()]
         if len(matches) == 1:
             return matches[0]
         return None

model_tools.py

@@ -101,7 +101,7 @@ def _discover_tools():
         try:
             importlib.import_module(mod_name)
         except Exception as e:
-            logger.debug("Could not import %s: %s", mod_name, e)
+            logger.warning("Could not import tool module %s: %s", mod_name, e)
 
 
 _discover_tools()