ruff (#169)

* polish: streamline nav, extract inline styles, improve tablet UX

- Restructure desktop nav from 8+ flat links + overflow dropdown into
  5 grouped dropdowns (Core, Agents, Intel, System, More) matching
  the mobile menu structure to reduce decision fatigue
- Extract all inline styles from mission_control.html and base.html
  notification elements into mission-control.css with semantic classes
- Replace JS-built innerHTML with secure DOM construction in
  notification loader and chat history
- Add CONNECTING state to connection indicator (amber) instead of
  showing OFFLINE before WebSocket connects
- Add tablet breakpoint (1024px) with larger touch targets for
  Apple Pencil / stylus use and safe-area padding for iPad toolbar
- Add active-link highlighting in desktop dropdown menus
- Rename "Mission Control" page title to "System Overview" to
  disambiguate from the chat home page
- Add "Home — Timmy Time" page title to index.html

https://claude.ai/code/session_015uPUoKyYa8M2UAcyk5Gt6h

* fix(security): move auth-gate credentials to environment variables

Hardcoded username, password, and HMAC secret in auth-gate.py replaced
with os.environ lookups. Startup now refuses to run if any variable is
unset. Added AUTH_GATE_SECRET/USER/PASS to .env.example.

https://claude.ai/code/session_015uPUoKyYa8M2UAcyk5Gt6h

* refactor(tooling): migrate from black+isort+bandit to ruff

Replace three separate linting/formatting tools with a single ruff
invocation. Updates tox.ini (lint, format, pre-push, pre-commit envs),
.pre-commit-config.yaml, and CI workflow. Fixes all ruff errors
including unused imports, missing raise-from, and undefined names.
Ruff config maps existing bandit skips to equivalent S-rules.

https://claude.ai/code/session_015uPUoKyYa8M2UAcyk5Gt6h

---------

Co-authored-by: Claude <noreply@anthropic.com>

tests/infrastructure/test_event_bus.py

@@ -173,7 +173,7 @@ class TestEventBus:
 
     async def test_history_limit(self):
         bus = self._fresh_bus()
-        for i in range(5):
+        for _i in range(5):
             await bus.publish(Event(type="h.x", source="s"))
 
         assert len(bus.get_history(limit=3)) == 3
@@ -181,7 +181,7 @@ class TestEventBus:
     async def test_history_max_cap(self):
         bus = self._fresh_bus()
         bus._max_history = 10
-        for i in range(15):
+        for _i in range(15):
             await bus.publish(Event(type="cap", source="s"))
 
         assert len(bus._history) == 10
@@ -302,7 +302,7 @@ class TestEventBusPersistence:
 
     async def test_replay_respects_limit(self, persistent_bus):
         """Replay should respect the limit parameter."""
-        for i in range(10):
+        for _i in range(10):
             await persistent_bus.publish(Event(type="x", source="s"))
 
         events = persistent_bus.replay(limit=3)