feat: migrate to OpenCode SDK v2

Update all import statements to use @opencode-ai/sdk/v2
Modify Vite configurations to alias new SDK path
Update API client method signatures for SDK v2 compatibility

packages/ui/src/components/chat/message/partUtils.ts

@@ -1,4 +1,4 @@
-import type { Part } from '@opencode-ai/sdk';
+import type { Part } from '@opencode-ai/sdk/v2';
 
 type PartWithText = Part & { text?: string; content?: string; value?: string };