feat(opencode): migrate agent runtime to v2

.opencode/tools/defineTool.ts

@@ -0,0 +1,31 @@
+import { z } from "zod";
+
+type ToolContext = {
+  sessionID: string;
+};
+
+type ToolDefinition<Shape extends z.ZodRawShape> = {
+  description: string;
+  args: Shape;
+  execute: (
+    args: z.infer<z.ZodObject<Shape>>,
+    context: ToolContext,
+  ) => Promise<string> | string;
+};
+
+const defineTool = <Shape extends z.ZodRawShape>(
+  definition: ToolDefinition<Shape>,
+) => {
+  const inputSchema = z.object(definition.args);
+  return {
+    description: definition.description,
+    input: z.toJSONSchema(inputSchema),
+    async execute(input: unknown, context: ToolContext) {
+      return {
+        content: await definition.execute(inputSchema.parse(input), context),
+      };
+    },
+  };
+};
+
+export const tool = Object.assign(defineTool, { schema: z });