feat: implement full context-scoped AI chat UI in AIChatPanel

- Added AIChatPanel component with context header, user and AI message handling.
- Integrated streaming responses via IPC and error handling for chat mutations.
- Enhanced user experience with input handling and auto-scrolling features.
- Updated AppShell to derive AI chat context from the current route.
- Introduced ScrollArea component for better scrolling behavior in various dialogs.
- Added support for Tailwind typography and improved global styles.
- Updated project and task dialogs to utilize ScrollArea for better UX.

prd.json

@@ -370,8 +370,8 @@
         "Verify in browser using dev-browser skill"
       ],
       "priority": 20,
-      "passes": false,
-      "notes": ""
+      "passes": true,
+      "notes": "Completed: Full chat UI in AIChatPanel with context header Badge, user Card bubbles, AI plain text (Sparkles+Adiuva header), streaming via IPC, Skeleton loading, error Cards, session-only history cleared on curtain close"
     },
     {
       "id": "US-021",