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/services/spec_chat_session.py

@@ -179,15 +179,10 @@ class SpecChatSession:
                     model=model,
                     cli_path=system_cli,
                     # System prompt loaded from CLAUDE.md via setting_sources
-                    # This avoids Windows command line length limit (~8191 chars)
-                    setting_sources=["project"],
-                    allowed_tools=[
-                        "Read",
-                        "Write",
-                        "Edit",
-                        "Glob",
-                    ],
-                    permission_mode="acceptEdits",  # Auto-approve file writes for spec creation
+                    # Include "user" for global skills and subagents from ~/.claude/
+                    setting_sources=["project", "user"],
+                    # No allowed_tools restriction - full access to all tools, skills, subagents
+                    permission_mode="bypassPermissions",  # Auto-approve all tools
                     max_turns=100,
                     cwd=str(self.project_dir.resolve()),
                     settings=str(settings_file.resolve()),