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/run.py

@@ -220,7 +220,7 @@ from gateway.session import (
     build_session_context_prompt,
     build_session_key,
 )
-from gateway.delivery import DeliveryRouter, DeliveryTarget
+from gateway.delivery import DeliveryRouter
 from gateway.platforms.base import BasePlatformAdapter, MessageEvent, MessageType
 
 logger = logging.getLogger(__name__)
@@ -2771,8 +2771,6 @@ class GatewayRunner:
         """Handle /model command - show or change the current model."""
         import yaml
         from hermes_cli.models import (
-            parse_model_input,
-            validate_requested_model,
             curated_models_for_provider,
             normalize_provider,
             _PROVIDER_LABELS,