chore: remove ~100 unused imports across 55 files (#3016)

Automated cleanup via pyflakes + autoflake with manual review.

Changes:
- Removed unused stdlib imports (os, sys, json, pathlib.Path, etc.)
- Removed unused typing imports (List, Dict, Any, Optional, Tuple, Set, etc.)
- Removed unused internal imports (hermes_cli.auth, hermes_cli.config, etc.)
- Fixed cli.py: removed 8 shadowed banner imports (imported from hermes_cli.banner
  then immediately redefined locally — only build_welcome_banner is actually used)
- Added noqa comments to imports that appear unused but serve a purpose:
  - Re-exports (gateway/session.py SessionResetPolicy, tools/terminal_tool.py
    is_interrupted/_interrupt_event)
  - SDK presence checks in try/except (daytona, fal_client, discord)
  - Test mock targets (auxiliary_client.py Path, mcp_config.py get_hermes_home)

Zero behavioral changes. Full test suite passes (6162/6162, 2 pre-existing
streaming test failures unrelated to this change).

gateway/session.py

@@ -16,7 +16,7 @@ import re
 import uuid
 from pathlib import Path
 from datetime import datetime, timedelta
-from dataclasses import dataclass, field
+from dataclasses import dataclass
 from typing import Dict, List, Optional, Any
 
 logger = logging.getLogger(__name__)
@@ -59,7 +59,7 @@ def _looks_like_phone(value: str) -> bool:
 from .config import (
     Platform,
     GatewayConfig,
-    SessionResetPolicy,
+    SessionResetPolicy,  # noqa: F401 — re-exported via gateway/__init__.py
     HomeChannel,
 )