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/rl_training_tool.py

@@ -567,7 +567,7 @@ async def rl_select_environment(name: str) -> str:
     
     TIP: Read the returned file_path to understand how the environment works.
     """
-    global _current_env, _current_config, _env_config_cache
+    global _current_env, _current_config
     
     _initialize_environments()
     
@@ -673,8 +673,6 @@ async def rl_edit_config(field: str, value: Any) -> str:
     Returns:
         JSON string with updated config or error message
     """
-    global _current_config
-    
     if not _current_env:
         return json.dumps({
             "error": "No environment selected. Use rl_select_environment(name) first.",
@@ -727,8 +725,6 @@ async def rl_start_training() -> str:
     Returns:
         JSON string with run_id and initial status
     """
-    global _active_runs
-    
     if not _current_env:
         return json.dumps({
             "error": "No environment selected. Use rl_select_environment(name) first.",
@@ -829,8 +825,6 @@ async def rl_check_status(run_id: str) -> str:
     Returns:
         JSON string with run status and metrics
     """
-    global _last_status_check
-    
     # Check rate limiting
     now = time.time()
     if run_id in _last_status_check:
@@ -1311,7 +1305,7 @@ async def rl_test_inference(
         "avg_accuracy": round(
             sum(m.get("accuracy", 0) for m in working_models) / len(working_models), 3
         ) if working_models else 0,
-        "environment_working": len(working_models) > 0,
+        "environment_working": bool(working_models),
         "output_directory": str(test_output_dir),
     }