refactor: unify RoleDefinition + WorkflowDefinition with description & schema

- Add RoleDefinition<Meta> = { description, run, schema } to core types
- WorkflowDefinition now carries description and RoleDefinition per role
- Add buildDescriptor() in core to derive WorkflowDescriptor from WorkflowDefinition
- Remove buildDescriptorFromRoles / RoleDescriptorInput from workflow-util-role
- Update solve-issue template, examples, and all tests

小橘 <xiaoju@shazhou.work>

examples/hello-world.ts

@@ -1,9 +1,14 @@
-import { createRoleModerator, END, type Role } from "@uncaged/workflow";
+import { createRoleModerator, END, type RoleDefinition } from "@uncaged/workflow";
+import * as z from "zod/v4";
 
 type Roles = {
   greeter: { greeting: string };
 };
 
+const greeterMetaSchema = z.object({
+  greeting: z.string(),
+});
+
 export const descriptor = {
   description: "A simple hello world workflow",
   roles: {
@@ -18,10 +23,14 @@ export const descriptor = {
   },
 };
 
-const greeter: Role<Roles["greeter"]> = async (ctx) => ({
-  content: `Hello, ${ctx.start.content}`,
-  meta: { greeting: "Hello!" },
-});
+const greeter: RoleDefinition<Roles["greeter"]> = {
+  description: "Generates a greeting",
+  schema: greeterMetaSchema,
+  run: async (ctx) => ({
+    content: `Hello, ${ctx.start.content}`,
+    meta: { greeting: "Hello!" },
+  }),
+};
 
 export const run = createRoleModerator<Roles>({
   roles: { greeter },

examples/package.json

@@ -3,6 +3,7 @@
   "private": true,
   "type": "module",
   "dependencies": {
-    "@uncaged/workflow": "workspace:*"
+    "@uncaged/workflow": "workspace:*",
+    "zod": "^4.0.0"
   }
 }