feat(adapter/cursor): Cursor Composer / Agent CLI skill runtime

[potiuk]

Goal: Bring Cursor (Composer + Agent + CLI) to feature parity with Claude Code as a skill runtime. Grounds: RFC-AI-0004 Principle 3 + the RFC's adoption checklist, which names Cursor's Composer by name as a host that "supports per-action confirmation".

Why Cursor: Largest market share in the IDE-agent space; many OSS maintainers already use it as their primary editor. Reaching parity means a maintainer can run framework skills without leaving their editor. Cursor's recent CLI mode (cursor-agent / background agents) makes non-IDE invocation viable.

What "parity" means:

• Skills under .claude/skills/<name>/SKILL.md are invokable from Cursor (both IDE Composer and CLI Agent mode)
• The tools/* bridges are reachable
• Sandbox parity: Cursor's "Auto-Run" allow / deny rules map to the framework's command-permission discipline; document the equivalence
• HITL primitives: Cursor's per-action confirmation is the native fit; document the wiring for the framework's "draft before send" rule

Suggested approach:

• Map SKILL.md → Cursor's .cursor/rules/ rule format (Cursor's project-rules mechanism is the closest equivalent to skills)
• For the Agent CLI mode, document the skill-invocation pattern (cursor-agent <skill-prompt>)
• Map sandbox parity to Cursor's Auto-Run allowlist + the framework's setup-isolated-* baseline
• Validate that Cursor's MCP support covers the framework's MCP-shaped tools

Reference:

• RFC-AI-0004: docs/rfcs/RFC-AI-0004.md
• Cursor docs: https://docs.cursor.com/
• Cursor rules: https://docs.cursor.com/context/rules
• Existing skill shape: .claude/skills/