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.

DEFAULT_PROMPT.md

@@ -1,4 +1,4 @@
-## Your Task
+## Your Task US-020
 
 1. Read the full app PRD at `prd-main.md` (in the same directory as this file)
 2. Read the PRD at `prd.json` (in the same directory as this file)
@@ -23,19 +23,22 @@ APPEND to progress.txt (never replace, always append):
 
 ## USER REQUEST
 {
-  "id": "US-018",
-  "title": "GitHub Copilot SDK setup and keytar token storage",
-  "description": "As a developer, I need the GitHub Copilot SDK initialized in the main process with secure OS keychain token storage so that AI features can authenticate.",
+  "id": "US-020",
+  "title": "Context-scoped AI chat UI",
+  "description": "As a user, I want the AI chat (revealed by the Fluid Curtain) to display a context header, support message input, and stream AI responses.",
   "acceptanceCriteria": [
-    "keytar installed and imported in main process only (not renderer)",
-    "ai.setToken tRPC mutation accepts { token: string } and stores it via keytar.setPassword('adiuva', 'copilot-token', token)",
-    "ai.hasToken tRPC query returns a boolean indicating whether a token is stored",
-    "On app start, main process reads the token from keychain and initializes the GitHub Copilot SDK client",
-    "Settings dialog uses shadcn/ui Dialog (DialogTrigger as a SidebarMenuButton with Settings/gear icon in the sidebar footer); dialog content uses shadcn/ui Input for token paste + shadcn/ui Button to save via ai.setToken",
-    "If no token is stored, AI-dependent features display a prompt using shadcn/ui Card with a shadcn/ui Button linking to the Settings dialog instead of throwing an error",
-    "Typecheck passes"
+    "Chat panel shows a context header using shadcn/ui Badge (variant=outline): 'Chatting about: [Project Name]' when opened from a project detail view, or 'Global workspace' when opened from other sections",
+    "Chat input box uses shadcn/ui Textarea: white background, border #d4d4d4, shadow-lg, min-height 109px, placeholder 'Ask me anything...'; Send uses shadcn/ui Button (black bg, Send Lucide icon + 'Send' label) anchored bottom-right",
+    "User messages appear as right-aligned message bubbles using shadcn/ui Card; AI responses as left-aligned Cards",
+    "Streaming: AI response tokens appended to the current AI bubble as they arrive from ai.chat",
+    "A loading spinner or pulsing indicator (shadcn/ui Skeleton) shown while waiting for first token",
+    "If ai.chat returns { error }, display the error message in a shadcn/ui Card with destructive border styling",
+    "Chat history is session-only — cleared when the curtain closes or the app restarts",
+    "Install shadcn/ui components via 'npx shadcn@latest add textarea' before implementing (card, badge, button, skeleton already installed)",
+    "Typecheck passes",
+    "Verify in browser using dev-browser skill"
   ],
-  "priority": 18,
+  "priority": 20,
   "passes": false,
   "notes": ""
 }