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/stores/utils/messageUtils.ts

@@ -1,4 +1,4 @@
-import type { Part } from "@opencode-ai/sdk";
+import type { Part } from "@opencode-ai/sdk/v2";
 
 const extractTextFromDelta = (delta: unknown): string => {
     if (!delta) return '';

packages/ui/src/stores/utils/tokenUtils.ts

@@ -1,4 +1,4 @@
-import type { Message, Part } from "@opencode-ai/sdk";
+import type { Message, Part } from "@opencode-ai/sdk/v2";
 
 type TokenBreakdown = {
     input?: number;