feat: add "Create Spec" button and fix Windows asyncio subprocess

UI Changes:
- Add "Create Spec with AI" button in empty kanban when project has no spec
- Button opens SpecCreationChat to guide users through spec creation
- Shows in Pending column when has_spec=false and no features exist

Windows Fixes:
- Fix asyncio subprocess NotImplementedError on Windows
- Set WindowsProactorEventLoopPolicy in server/__init__.py
- Remove --reload from uvicorn (incompatible with Windows subprocess)
- Add process cleanup on startup in start_ui.bat

Spec Chat Improvements:
- Enable full tool access (remove allowed_tools restriction)
- Add "user" to setting_sources for global skills access
- Use bypassPermissions mode for auto-approval
- Add WebFetch/WebSearch auto-approve hook

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

ui/src/components/KanbanBoard.tsx

@@ -7,9 +7,11 @@ interface KanbanBoardProps {
   onAddFeature?: () => void
   onExpandProject?: () => void
   activeAgents?: ActiveAgent[]
+  onCreateSpec?: () => void  // Callback to start spec creation
+  hasSpec?: boolean          // Whether the project has a spec
 }
 
-export function KanbanBoard({ features, onFeatureClick, onAddFeature, onExpandProject, activeAgents = [] }: KanbanBoardProps) {
+export function KanbanBoard({ features, onFeatureClick, onAddFeature, onExpandProject, activeAgents = [], onCreateSpec, hasSpec = true }: KanbanBoardProps) {
   const hasFeatures = features && (features.pending.length + features.in_progress.length + features.done.length) > 0
 
   // Combine all features for dependency status calculation
@@ -47,6 +49,8 @@ export function KanbanBoard({ features, onFeatureClick, onAddFeature, onExpandPr
         onAddFeature={onAddFeature}
         onExpandProject={onExpandProject}
         showExpandButton={hasFeatures}
+        onCreateSpec={onCreateSpec}
+        showCreateSpec={!hasSpec && !hasFeatures}
       />
       <KanbanColumn
         title="In Progress"