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>

packages/workflow-util-role/__tests__/create-role.test.ts

@@ -42,8 +42,8 @@ function makeCtx(): ThreadContext {
       meta: { maxRounds: 10 },
       timestamp: Date.now(),
     },
-      steps: [],
-      threadId: "01TEST000000000000000000TR",
+    steps: [],
+    threadId: "01TEST000000000000000000TR",
   };
 }