Add Causely Cursor Marketplace plugin

[enlinxu]

Adds the complete plugin package for submission to the Cursor Marketplace.

What's included

Plugin manifest (.cursor-plugin/plugin.json) — registers the plugin with name, version, description, author, and keywords for Cursor's discovery and search.

MCP server (mcp.json) — connects to the hosted Causely MCP server at https://api.causely.app/mcp over Streamable HTTP. Supports both OAuth (browser sign-in) and API
credentials (X-Causely-Client-Basic header) for non-interactive environments.

Six packaged skills under skills/ — each skill activates automatically for the right type of question and carries a shared references/complete-investigation.md grounded
in Causely's full tool inventory:

• causely-alert-triage — map incoming alerts to root causes
• causely-change-impact — post-deploy regression and blast radius analysis
• causely-correlated-incidents — multi-service failure correlation
• causely-health-reporting — health summaries, SLO status, morning briefings
• causely-k8s-investigation — Kubernetes infrastructure deep-dives
• causely-postmortem — structured post-mortems and ticket drafts

Supporting files — README.md with installation and usage guide, CHANGELOG.md for v1.0.0, LICENSE (Apache 2.0), and logo.svg.

Notes

• All MCP tools are read-only. Causely does not execute changes through this connection.
• Skills are auto-discovered by Cursor from the skills/ directory — no explicit paths needed in plugin.json.
• Structure follows the established vendor pattern (e.g. datadog-labs/cursor-plugin).