refactor!: remove deprecated Agent types, introduce Adapter-first API

BREAKING CHANGES:
- Remove AgentFn, AgentFnResult, AgentBinding from workflow-protocol
- Remove wrapAgentAsAdapter from workflow-util-agent
- workflowAsAgent → workflowAdapter (old name kept as deprecated re-export)

New APIs:
- createTextAdapter(producer) — bridges text-producing functions to AdapterFn
- TextProducerFn, TextAdapterResult types
- workflowAdapter() — direct AdapterFn for child workflow delegation

All agent packages (cursor, hermes, llm) now return AdapterFn directly,
no wrapping needed. Bundle entries simplified accordingly.

小橘 🍊（NEKO Team）

packages/workflow-agent-hermes/__tests__/hermes-agent.test.ts

@@ -37,7 +37,7 @@ describe("validateHermesAgentConfig", () => {
 });
 
 describe("createHermesAgent", () => {
-  test("returns an AgentFn even with invalid config (validation deferred to call)", () => {
+  test("returns an AdapterFn even with invalid config (validation deferred to call)", () => {
     const agent = createHermesAgent({
       command: "/usr/local/bin/hermes",
       model: null,