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-runtime/src/index.ts

@@ -4,10 +4,7 @@ export { err, ok } from "./result.js";
 export type {
   AdapterBinding,
   AdapterFn,
-  AgentBinding,
   AgentContext,
-  AgentFn,
-  AgentFnResult,
   CasStore,
   ExtractFn,
   ExtractResult,

packages/workflow-runtime/src/types.ts

@@ -6,10 +6,7 @@ export type {
   AdapterBinding,
   AdapterFn,
   AdvanceOutcome,
-  AgentBinding,
   AgentContext,
-  AgentFn,
-  AgentFnResult,
   CasStore,
   ExtractFn,
   ExtractResult,