fix: make display_hermes_home imports lazy to prevent ImportError during hermes update (#3776)

When a user runs 'hermes update', the Python process caches old modules
in sys.modules.  After git pull updates files on disk, lazy imports of
newly-updated modules fail because they try to import display_hermes_home
from the cached (old) hermes_constants which doesn't have the function.

This specifically broke the gateway auto-restart in cmd_update — importing
hermes_cli/gateway.py triggered the top-level 'from hermes_constants
import display_hermes_home' against the cached old module.  The ImportError
was silently caught, so the gateway was never restarted after update.

Users with a running gateway then hit the ImportError on their next
Telegram/Discord message when the stale gateway process lazily loaded
run_agent.py (new version) which also had the top-level import.

Fixes:
- hermes_cli/gateway.py: lazy import at call site (line 940)
- run_agent.py: lazy import at call site (line 6927)
- tools/terminal_tool.py: lazy imports at 3 call sites
- tools/tts_tool.py: static schema string (no module-level call)
- hermes_cli/auth.py: lazy import at call site (line 2024)
- hermes_cli/main.py: reload hermes_constants after git pull in cmd_update

Also fixes 4 pre-existing test failures in test_parse_env_var caused by
NameError on display_hermes_home in terminal_tool.py.

tools/tts_tool.py

@@ -33,7 +33,7 @@ import subprocess
 import tempfile
 import threading
 from pathlib import Path
-from hermes_constants import get_hermes_home, display_hermes_home
+from hermes_constants import get_hermes_home
 from typing import Callable, Dict, Any, Optional
 
 logger = logging.getLogger(__name__)
@@ -832,7 +832,7 @@ TTS_SCHEMA = {
             },
             "output_path": {
                 "type": "string",
-                "description": f"Optional custom file path to save the audio. Defaults to {display_hermes_home()}/cache/audio/<timestamp>.mp3"
+                "description": "Optional custom file path to save the audio. Defaults to ~/.hermes/audio_cache/<timestamp>.mp3"
             }
         },
         "required": ["text"]