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.

gateway/run.py

@@ -24,7 +24,6 @@ import signal
 import tempfile
 import threading
 import time
-import uuid
 from pathlib import Path
 from datetime import datetime
 from typing import Dict, Optional, Any, List
@@ -378,7 +377,7 @@ def _check_unavailable_skill(command_name: str) -> str | None:
                     )
 
         # Check optional skills (shipped with repo but not installed)
-        from hermes_constants import get_hermes_home, get_optional_skills_dir
+        from hermes_constants import get_optional_skills_dir
         repo_root = Path(__file__).resolve().parent.parent
         optional_dir = get_optional_skills_dir(repo_root / "optional-skills")
         if optional_dir.exists():
@@ -2822,7 +2821,7 @@ class GatewayRunner:
                         guessed, _ = _mimetypes.guess_type(path)
                         if guessed:
                             mtype = guessed
-                if not (mtype.startswith("application/") or mtype.startswith("text/")):
+                if not mtype.startswith(("application/", "text/")):
                     continue
                 # Extract display filename by stripping the doc_{uuid12}_ prefix
                 import os as _os
@@ -3909,7 +3908,7 @@ class GatewayRunner:
 
             return f"🎭 Personality set to **{args}**\n_(takes effect on next message)_"
 
-        available = "`none`, " + ", ".join(f"`{n}`" for n in personalities.keys())
+        available = "`none`, " + ", ".join(f"`{n}`" for n in personalities)
         return f"Unknown personality: `{args}`\n\nAvailable: {available}"
     
     async def _handle_retry_command(self, event: MessageEvent) -> str:
@@ -5321,9 +5320,6 @@ class GatewayRunner:
                 old_servers = set(_servers.keys())
 
             # Read new config before shutting down, so we know what will be added/removed
-            new_config = _load_mcp_config()
-            new_server_names = set(new_config.keys())
-
             # Shutdown existing connections
             await loop.run_in_executor(None, shutdown_mcp_servers)
 
@@ -5411,7 +5407,6 @@ class GatewayRunner:
 
         from tools.approval import (
             resolve_gateway_approval, has_blocking_approval,
-            pending_approval_count,
         )
 
         if not has_blocking_approval(session_key):