Add Omneky hosted MCP plugin

[ganesh-omneky]

What this PR does

Adds the Omneky plugin so Grok Build can connect to Omneky's hosted MCP.

• Plugin name: omneky
• Type: local (external_plugins)
• Source URL + pinned SHA (remote), or vendored path (local): ./external_plugins/omneky
• Homepage: https://www.omneky.com

The plugin is an HTTP MCP pointer at https://mcp.omneky.com/mcp. On install, Grok runs Omneky's OAuth 2.1 flow (dynamic client registration + browser sign-in). No API key, no local process, no server source.

Ownership

• I own this plugin or have the right to distribute it.
• The source repo is published under our official org (or I've explained why not below).

Vendored under external_plugins/omneky/ from Omneky (omneky-org). We do not remote-source our MCP server repo — that repo is private and is not what Grok should clone.

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. (n/a — local source)
• 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 (and why):
  • https://mcp.omneky.com/mcp — hosted MCP (streamable HTTP)
  • https://mcp.omneky.com/authorize, /token, /register — OAuth 2.1 + DCR (discovered via /.well-known/oauth-authorization-server)
  • https://cgp.omneky.com/login — human sign-in (password / Google), then resume on mcp.omneky.com
• Credentials/permissions it requires (and why):
  • Omneky account via browser OAuth. The access token is an Omneky Nexus JWT used as Authorization: Bearer on /mcp. No API key in the plugin. Tools are scoped to brands the signed-in user can access.

Notes for reviewers

Omneky is an ads platform (analytics, product catalogue, multi-channel launch, creative generation). Official org: https://github.com/omneky-org. Product: https://www.omneky.com.

This listing is the same hosted MCP already used by Claude / ChatGPT, at the full /mcp surface. We are not submitting /mcp-claude (that path exists only for Anthropic's Connector Directory review).

Keywords are brand-scoped (omneky, omneky ads, omneky mcp) so the plugin CTA does not fire on generic “ads” / “mcp” prompts.