feat: add apify plugin

[Jakub-Vacek]

What this PR does

This PR adds new Apify plugin (Apify MCP config, 5 skills and 1 agent) that allows users to extract data from any website with thousands of trusted scrapers, crawlers, and automations from Apify Store. It also allows user to build, debug, publish, and monetize new Actors on Apify. I tested the plugin locally + through remote marketplace and it works well (MCP tested with OAuth flow).

• Plugin name: Apify
• Type: remote source
• Source URL: https://github.com/apify/apify-grok-build-plugin a90e598fb28a9c0e1a30f0c649d528bd3d27f600
• Homepage: https://apify.com

Ownership

• I own this plugin or have the right to distribute it.
• The source repo is published under our official org.

Checklist

• Added/updated exactly one entry in .grok-plugin/marketplace.json (valid JSON, kebab-case name).
• Remote source pins a full 40-char lowercase commit sha, and that commit is public + reachable.
• Regenerated .grok-plugin/plugin-index.json (python3 scripts/generate-plugin-index.py).
• python3 scripts/validate-catalog.py passes locally.
• python3 scripts/generate-plugin-index.py --check passes locally.
• homepage + clear description set; local plugins include README.md + .grok-plugin/plugin.json.
• License is stated.

Security

• No curl | bash, remote-code download/exec, or postinstall RCE.
• No reading/exfiltration of secrets, tokens, .env, or env vars.
• Hooks and MCP scope are least-privilege.
• Network endpoints this plugin calls: only Apify API is used through Apify MCP
• Credentials/permissions it requires: User needs Apify account (Apify has actually usable free plan) to use run the actors. There are no special permissions required.

Notes for reviewers

Let me know if anything is missing or incorrect, I will address it ASAP :)