Add Cursor CLI as target provider (#179)

* feat(cursor): add Cursor CLI as target provider

Add converter, writer, types, and tests for converting Claude Code
plugins to Cursor-compatible format (.mdc rules, commands, skills,
mcp.json). Agents become Agent Requested rules (alwaysApply: false),
commands are plain markdown, skills copy directly, MCP is 1:1 JSON.

* docs: add Cursor spec and update README with cursor target

* chore: bump CLI version to 0.5.0 for cursor target

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* docs: note Cursor IDE + CLI compatibility in README

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@every-env/compound-plugin",
-  "version": "0.4.0",
+  "version": "0.5.0",
   "type": "module",
   "private": false,
   "bin": {