refactor: all-agentic architecture — roles as pure data, agent binding at runtime

BREAKING: Major architecture change.

- RoleDefinition = pure data (systemPrompt + schema + dryRunMeta)
- AgentFn = (ctx: ThreadContext) => Promise<string>, reads ctx.currentRole
- WorkflowDefinition decoupled from agents, bound via AgentBinding at runtime
- createWorkflow(def, binding, extract) replaces createRoleModerator
- Meta extraction moved into engine loop
- Delete workflow-util-role package (createRole, decorators, extract all gone)
- Role packages become pure data exports
- Agent packages updated to single-arg AgentFn

小橘 <xiaoju@shazhou.work>

examples/hello-world.ts

@@ -1,4 +1,4 @@
-import { createRoleModerator, END, type RoleDefinition } from "@uncaged/workflow";
+import { createWorkflow, END, type RoleDefinition } from "@uncaged/workflow";
 import * as z from "zod/v4";
 
 type Roles = {
@@ -25,16 +25,25 @@ export const descriptor = {
 
 const greeter: RoleDefinition<Roles["greeter"]> = {
   description: "Generates a greeting",
+  systemPrompt: "You greet the user briefly.",
   schema: greeterMetaSchema,
-  run: async (ctx) => ({
-    content: `Hello, ${ctx.start.content}`,
-    meta: { greeting: "Hello!" },
-  }),
+  dryRunMeta: { greeting: "Hello!" },
 };
 
-export const run = createRoleModerator<Roles>({
-  roles: { greeter },
-  moderator(ctx) {
-    return ctx.steps.length === 0 ? "greeter" : END;
+const extract = {
+  provider: { baseUrl: "http://127.0.0.1:9", apiKey: "", model: "" },
+  dryRun: true,
+} as const;
+
+export const run = createWorkflow<Roles>(
+  {
+    roles: { greeter },
+    moderator(ctx) {
+      return ctx.steps.length === 0 ? "greeter" : END;
+    },
   },
-});
+  {
+    agent: async (ctx) => `Hello, ${ctx.start.content}`,
+  },
+  extract,
+);