refactor(agent-kit): base AgentContext on ModeratorContext

AgentContext now extends ModeratorContext (start + steps) with threadId, role, store, and expanded workflow. Hermes and mock-agent read prompt/steps/systemPrompt from the new shape.

Co-authored-by: Cursor <cursoragent@cursor.com>

scripts/mock-agent.ts

@@ -16,7 +16,7 @@ const MOCK_RAW_OUTPUT_SCHEMA: JSONSchema = {
 const agent = createAgent({
   name: "mock",
   run: async (ctx) => {
-    const output = `Mock output for role ${ctx.role}: task was "${ctx.prompt}"`;
+    const output = `Mock output for role ${ctx.role}: task was "${ctx.start.prompt}"`;
     const { store } = ctx;
     await bootstrap(store);
     const schemaHash = await putSchema(store, MOCK_RAW_OUTPUT_SCHEMA);