dify: AI-optimize MCP action set

Dify has no actions built in Pipedream today — there's nothing an agent can do with this integration yet. We'd like to build an initial action set so an agent can manage LLM apps and workflows, and so each tool is easy for an agent to configure.

A few things an agent can't do today, for example:
- Send a message to a chat app
- Run a workflow
- Query a knowledge base
- List conversations

**API reference:** https://docs.dify.ai/en/use-dify/publish/developing-with-apis

**Add marker:**
When a component is AI-optimized, add this as the first line of the file:
```
// x-pd-ai: optimized
```
Add it to each action file and to the app's `.mjs` file.