Add Statsig third-party MCP plugin

[SamSokolin]

Summary

Packages Statsig's official remote MCP server as a marketplace / Grok Bot connector plugin at third_party/statsig/, following the existing third-party OAuth HTTP pattern (Attio #339, Clay, Intercom, Calendly).

Related to EXTY-1365 (https://linear.app/anysphere/issue/EXTY-1365/agents-have-no-single-reliable-path-to-read-statsig) — that ticket covers broader skill routing; this PR is the public HTTP connector packaging slice.

Originating ask: xai-fte Slack, channel C0BQKE29LNP, thread p1789255395993009.

What's in the plugin

• mcp.json — URL-only Streamable HTTP config pointing at Statsig's hosted endpoint. Auth is OAuth; Cursor handles the sign-in on first use. No secrets, client IDs, or env templates.

{
  "mcpServers": {
    "statsig": {
      "type": "http",
      "url": "https://api.statsig.com/v1/mcp"
    }
  }
}

• .cursor-plugin/plugin.json — name: statsig, category: integrations, author Cursor / plugins@cursor.com, homepage → https://docs.statsig.com/integrations/mcp/cursor, mcpServers: ./mcp.json. Fields mirror Attio's manifest.
• README.md — install steps, MCP config, prerequisites (Statsig org owner must enable Personal Console API Keys for the user's role; OAuth only supports those), capabilities table, notes.
• LICENSE (MIT), CHANGELOG.md (1.0.0).
• assets/logo.png — Statsig's official hexagon mark from the statsig-io GitHub org, resized to 192×192 RGBA PNG like Attio.

Registration

• Added statsig entry to .cursor-plugin/marketplace.json.
• Added statsig row to the root README.md plugins table.

Not included (by design)

• No npx mcp-remote / Console API key stdio alternative — the docs list it as a fallback, but this plugin ships the recommended OAuth HTTP setup only.
• Packaging only. Marketplace publish after merge is a separate step.

Verification

• Confirmed Statsig was not already packaged (no third_party/statsig, no marketplace entry).
• npm install --no-save ajv ajv-formats && node scripts/validate-plugins.mjs → All plugins validated successfully.
• Source of truth for URL and auth: https://docs.statsig.com/integrations/mcp/cursor and https://docs.statsig.com/integrations/mcp/manual-setup.