feat: add optional llm-task JSON-only tool (#1498)

* feat(llm-task): add optional JSON-only LLM task tool

* fix(llm-task): fix invalid package.json

* fix(llm-task): fix invalid plugin manifest JSON

* fix(llm-task): fix index.ts import quoting

* fix(llm-task): load embedded runner from src or bundled dist

extensions/llm-task/index.ts

@@ -0,0 +1,5 @@
+import { createLlmTaskTool } from "./src/llm-task-tool.js";
+
+export default function (api: any) {
+  api.registerTool(createLlmTaskTool(api), { optional: true });
+}