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>

server/__init__.py

@@ -6,3 +6,12 @@ Web UI server for the Autonomous Coding Agent.
 Provides REST API and WebSocket endpoints for project management,
 feature tracking, and agent control.
 """
+
+# Fix Windows asyncio subprocess support - MUST be before any other imports
+# that might create an event loop
+import sys
+
+if sys.platform == "win32":
+    import asyncio
+
+    asyncio.set_event_loop_policy(asyncio.WindowsProactorEventLoopPolicy())