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>

docs/specs/cursor.md

@@ -0,0 +1,85 @@
+# Cursor Spec (Rules, Commands, Skills, MCP)
+
+Last verified: 2026-02-12
+
+## Primary sources
+
+```
+https://docs.cursor.com/context/rules
+https://docs.cursor.com/context/rules-for-ai
+https://docs.cursor.com/customize/model-context-protocol
+```
+
+## Config locations
+
+| Scope | Path |
+|-------|------|
+| Project rules | `.cursor/rules/*.mdc` |
+| Project commands | `.cursor/commands/*.md` |
+| Project skills | `.cursor/skills/*/SKILL.md` |
+| Project MCP | `.cursor/mcp.json` |
+| Project CLI permissions | `.cursor/cli.json` |
+| Global MCP | `~/.cursor/mcp.json` |
+| Global CLI config | `~/.cursor/cli-config.json` |
+| Legacy rules | `.cursorrules` (deprecated) |
+
+## Rules (.mdc files)
+
+- Rules are Markdown files with the `.mdc` extension stored in `.cursor/rules/`.
+- Each rule has YAML frontmatter with three fields: `description`, `globs`, `alwaysApply`.
+- Rules have four activation types based on frontmatter configuration:
+
+| Type | `alwaysApply` | `globs` | `description` | Behavior |
+|------|:---:|:---:|:---:|---|
+| Always | `true` | ignored | optional | Included in every conversation |
+| Auto Attached | `false` | set | optional | Included when matching files are in context |
+| Agent Requested | `false` | empty | set | AI decides based on description relevance |
+| Manual | `false` | empty | empty | Only included via `@rule-name` mention |
+
+- Precedence: Team Rules > Project Rules > User Rules > Legacy `.cursorrules` > `AGENTS.md`.
+
+## Commands (slash commands)
+
+- Custom commands are Markdown files stored in `.cursor/commands/`.
+- Commands are plain markdown with no YAML frontmatter support.
+- The filename (without `.md`) becomes the command name.
+- Commands are invoked by typing `/` in the chat UI.
+- Commands support parameterized arguments via `$1`, `$2`, etc.
+
+## Skills (Agent Skills)
+
+- Skills follow the open SKILL.md standard, identical to Claude Code and Codex.
+- A skill is a folder containing `SKILL.md` plus optional `scripts/`, `references/`, and `assets/`.
+- `SKILL.md` uses YAML frontmatter with required `name` and `description` fields.
+- Skills can be repo-scoped in `.cursor/skills/` or user-scoped in `~/.cursor/skills/`.
+- At startup, only each skill's name/description is loaded; full content is injected on invocation.
+
+## MCP (Model Context Protocol)
+
+- MCP configuration lives in `.cursor/mcp.json` (project) or `~/.cursor/mcp.json` (global).
+- Each server is configured under the `mcpServers` key.
+- STDIO servers support `command` (required), `args`, and `env`.
+- Remote servers support `url` (required) and optional `headers`.
+- Cursor infers transport type from whether `command` or `url` is present.
+
+Example:
+
+```json
+{
+  "mcpServers": {
+    "server-name": {
+      "command": "npx",
+      "args": ["-y", "package-name"],
+      "env": { "KEY": "value" }
+    }
+  }
+}
+```
+
+## CLI (cursor-agent)
+
+- Cursor CLI launched August 2025 as `cursor-agent`.
+- Supports interactive mode, headless mode (`-p`), and cloud agents.
+- Reads `.cursor/rules/`, `.cursorrules`, and `AGENTS.md` for instructions.
+- CLI permissions controlled via `.cursor/cli.json` with allow/deny lists.
+- Permission tokens: `Shell(command)`, `Read(path)`, `Write(path)`, `Delete(path)`, `Grep(path)`, `LS(path)`.