feat: Add global settings modal and simplify agent controls

Adds a settings system for global configuration with YOLO mode toggle and
model selection. Simplifies the agent control UI by removing redundant
status indicator and pause functionality.

## Settings System
- New SettingsModal with YOLO mode toggle and model selection
- Settings persisted in SQLite (registry.db) - shared across all projects
- Models fetched from API endpoint (/api/settings/models)
- Single source of truth for models in registry.py - easy to add new models
- Optimistic UI updates with rollback on error

## Agent Control Simplification
- Removed StatusIndicator ("STOPPED"/"RUNNING" label) - redundant
- Removed Pause/Resume buttons - just Start/Stop toggle now
- Start button shows flame icon with fiery gradient when YOLO mode enabled

## Code Review Fixes
- Added focus trap to SettingsModal for accessibility
- Fixed YOLO button color contrast (WCAG AA compliance)
- Added model validation to AgentStartRequest schema
- Added model to AgentStatus response
- Added aria-labels to all icon-only buttons
- Added role="radiogroup" to model selection
- Added loading indicator during settings save
- Added SQLite timeout (30s) and retry logic with exponential backoff
- Added thread-safe database engine initialization
- Added orphaned lock file cleanup on server startup

## Files Changed
- registry.py: Model config, Settings CRUD, SQLite improvements
- server/routers/settings.py: New settings API
- server/schemas.py: Settings schemas with validation
- server/services/process_manager.py: Model param, orphan cleanup
- ui/src/components/SettingsModal.tsx: New modal component
- ui/src/components/AgentControl.tsx: Simplified to Start/Stop only

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

ui/src/App.tsx

@@ -16,7 +16,8 @@ import { DebugLogViewer } from './components/DebugLogViewer'
 import { AgentThought } from './components/AgentThought'
 import { AssistantFAB } from './components/AssistantFAB'
 import { AssistantPanel } from './components/AssistantPanel'
-import { Plus, Loader2 } from 'lucide-react'
+import { SettingsModal } from './components/SettingsModal'
+import { Plus, Loader2, Settings } from 'lucide-react'
 import type { Feature } from './lib/types'
 
 function App() {
@@ -34,10 +35,11 @@ function App() {
   const [debugOpen, setDebugOpen] = useState(false)
   const [debugPanelHeight, setDebugPanelHeight] = useState(288) // Default height
   const [assistantOpen, setAssistantOpen] = useState(false)
+  const [showSettings, setShowSettings] = useState(false)
 
   const { data: projects, isLoading: projectsLoading } = useProjects()
   const { data: features } = useFeatures(selectedProject)
-  const { data: agentStatusData } = useAgentStatus(selectedProject)
+  useAgentStatus(selectedProject) // Keep polling for status updates
   const wsState = useProjectWebSocket(selectedProject)
 
   // Play sounds when features move between columns
@@ -93,9 +95,17 @@ function App() {
         setAssistantOpen(prev => !prev)
       }
 
+      // , : Open settings
+      if (e.key === ',') {
+        e.preventDefault()
+        setShowSettings(true)
+      }
+
       // Escape : Close modals
       if (e.key === 'Escape') {
-        if (assistantOpen) {
+        if (showSettings) {
+          setShowSettings(false)
+        } else if (assistantOpen) {
           setAssistantOpen(false)
         } else if (showAddFeature) {
           setShowAddFeature(false)
@@ -109,7 +119,7 @@ function App() {
 
     window.addEventListener('keydown', handleKeyDown)
     return () => window.removeEventListener('keydown', handleKeyDown)
-  }, [selectedProject, showAddFeature, selectedFeature, debugOpen, assistantOpen])
+  }, [selectedProject, showAddFeature, selectedFeature, debugOpen, assistantOpen, showSettings])
 
   // Combine WebSocket progress with feature data
   const progress = wsState.progress.total > 0 ? wsState.progress : {
@@ -163,8 +173,16 @@ function App() {
                   <AgentControl
                     projectName={selectedProject}
                     status={wsState.agentStatus}
-                    yoloMode={agentStatusData?.yolo_mode ?? false}
                   />
+
+                  <button
+                    onClick={() => setShowSettings(true)}
+                    className="neo-btn text-sm py-2 px-3"
+                    title="Settings (,)"
+                    aria-label="Open Settings"
+                  >
+                    <Settings size={18} />
+                  </button>
                 </>
               )}
             </div>
@@ -270,6 +288,11 @@ function App() {
           />
         </>
       )}
+
+      {/* Settings Modal */}
+      {showSettings && (
+        <SettingsModal onClose={() => setShowSettings(false)} />
+      )}
     </div>
   )
 }