refactor: codebase-wide lint cleanup — unused imports, dead code, and inefficient patterns (#5821)

Comprehensive cleanup across 80 files based on automated (ruff, pyflakes, vulture)
and manual analysis of the entire codebase.

Changes by category:

Unused imports removed (~95 across 55 files):
- Removed genuinely unused imports from all major subsystems
- agent/, hermes_cli/, tools/, gateway/, plugins/, cron/
- Includes imports in try/except blocks that were truly unused
  (vs availability checks which were left alone)

Unused variables removed (~25):
- Removed dead variables: connected, inner, channels, last_exc,
  source, new_server_names, verify, pconfig, default_terminal,
  result, pending_handled, temperature, loop
- Dropped unused argparse subparser assignments in hermes_cli/main.py
  (12 instances of add_parser() where result was never used)

Dead code removed:
- run_agent.py: Removed dead ternary (None if False else None) and
  surrounding unreachable branch in identity fallback
- run_agent.py: Removed write-only attribute _last_reported_tool
- hermes_cli/providers.py: Removed dead @property decorator on
  module-level function (decorator has no effect outside a class)
- gateway/run.py: Removed unused MCP config load before reconnect
- gateway/platforms/slack.py: Removed dead SessionSource construction

Undefined name bugs fixed (would cause NameError at runtime):
- batch_runner.py: Added missing logger = logging.getLogger(__name__)
- tools/environments/daytona.py: Added missing Dict and Path imports

Unnecessary global statements removed (14):
- tools/terminal_tool.py: 5 functions declared global for dicts
  they only mutated via .pop()/[key]=value (no rebinding)
- tools/browser_tool.py: cleanup thread loop only reads flag
- tools/rl_training_tool.py: 4 functions only do dict mutations
- tools/mcp_oauth.py: only reads the global
- hermes_time.py: only reads cached values

Inefficient patterns fixed:
- startswith/endswith tuple form: 15 instances of
  x.startswith('a') or x.startswith('b') consolidated to
  x.startswith(('a', 'b'))
- len(x)==0 / len(x)>0: 13 instances replaced with pythonic
  truthiness checks (not x / bool(x))
- in dict.keys(): 5 instances simplified to in dict
- Redefined unused name: removed duplicate _strip_mdv2 import in
  send_message_tool.py

Other fixes:
- hermes_cli/doctor.py: Replaced undefined logger.debug() with pass
- hermes_cli/config.py: Consolidated chained .endswith() calls

Test results: 3934 passed, 17 failed (all pre-existing on main),
19 skipped. Zero regressions.

tools/terminal_tool.py

@@ -720,8 +720,6 @@ def _create_environment(env_type: str, image: str, cwd: str, timeout: int,
 
 def _cleanup_inactive_envs(lifetime_seconds: int = 300):
     """Clean up environments that have been inactive for longer than lifetime_seconds."""
-    global _active_environments, _last_activity
-
     current_time = time.time()
 
     # Check the process registry -- skip cleanup for sandboxes with active
@@ -784,8 +782,6 @@ def _cleanup_inactive_envs(lifetime_seconds: int = 300):
 
 def _cleanup_thread_worker():
     """Background thread worker that periodically cleans up inactive environments."""
-    global _cleanup_running
-
     while _cleanup_running:
         try:
             config = _get_env_config()
@@ -831,7 +827,7 @@ def get_active_environments_info() -> Dict[str, Any]:
     
     # Calculate total disk usage (per-task to avoid double-counting)
     total_size = 0
-    for task_id in _active_environments.keys():
+    for task_id in _active_environments:
         scratch_dir = _get_scratch_dir()
         pattern = f"hermes-*{task_id[:8]}*"
         import glob
@@ -848,8 +844,6 @@ def get_active_environments_info() -> Dict[str, Any]:
 
 def cleanup_all_environments():
     """Clean up ALL active environments. Use with caution."""
-    global _active_environments, _last_activity
-    
     task_ids = list(_active_environments.keys())
     cleaned = 0
     
@@ -877,8 +871,6 @@ def cleanup_all_environments():
 
 def cleanup_vm(task_id: str):
     """Manually clean up a specific environment by task_id."""
-    global _active_environments, _last_activity
-
     # Remove from tracking dicts while holding the lock, but defer the
     # actual (potentially slow) env.cleanup() call to outside the lock
     # so other tool calls aren't blocked.
@@ -1043,8 +1035,6 @@ def terminal_tool(
         # Force run after user confirmation
         # Note: force parameter is internal only, not exposed to model API
     """
-    global _active_environments, _last_activity
-
     try:
         # Get configuration
         config = _get_env_config()