feat(workflow): migrate supervisor to ThreadReactor (Phase 2)

- Rewrite supervisor to use createThreadReactor + createLlmFn
- No direct fetch/HTTP calls in supervisor
- All 266 tests passing

Refs #139, relates #141

packages/workflow-template-develop/__tests__/develop-template.test.ts

@@ -1,6 +1,6 @@
 import { describe, expect, test } from "bun:test";
-import { END, type ModeratorContext, type RoleStep, START } from "@uncaged/workflow-runtime";
 import { validateWorkflowDescriptor } from "@uncaged/workflow";
+import { END, type ModeratorContext, type RoleStep, START } from "@uncaged/workflow-runtime";
 import { buildDevelopDescriptor } from "../src/descriptor.js";
 import { developModerator } from "../src/index.js";
 import type { CommitterMeta, PlannerMeta } from "../src/roles/index.js";