docs: Add Cursor setup instructions for n8n skills plugin

[DawidMyslak]

Summary

Adds setup instructions for using n8n skills in Cursor to the plugin README and updates AGENTS.md with a callout for Cursor users pointing to the setup guide.

Cursor doesn't auto-discover plugins from .claude/plugins/ — users need to register the plugin manually in ~/.claude/plugins/installed_plugins.json. This documents the fix so both agents and developers can find it.

Related Linear tickets, Github issues, and Community forum posts

https://linear.app/n8n/issue/RLY-37

Review / Merge checklist

• I have seen this code, I have run this code, and I take responsibility for this code.
• PR title and summary are descriptive. (conventions)
• Docs updated or follow-up ticket created.
• Tests included.

[cubic-dev-ai]

No issues found across 2 files

Architecture diagram

sequenceDiagram
    participant Cursor as Cursor IDE
    participant Plugin as n8n Plugin (~/.claude/plugins/n8n)
    participant Registry as Plugin Registry (~/.claude/plugins/installed_plugins.json)
    participant Project as n8n Project (.claude/plugins/n8n/)
    
    Note over Cursor,Project: Cursor Plugin Discovery Flow
    
    Cursor->>Registry: Read installed_plugins.json
    Registry-->>Cursor: Plugin entries (name, path, version)
    
    alt Plugin NOT registered (n8n@n8n missing)
        Cursor->>Cursor: Skills not available
        Note over Cursor: User must manually register plugin
    else Plugin registered
        Cursor->>Project: Load skills/commands/agents from installPath
        Project-->>Cursor: Skill definitions (no n8n: prefix)
        Cursor->>Cursor: Make skills available in IDE
    end
    
    Note over Cursor,Project: User Workflow
    
    User->>Cursor: Invoke n8n skill (e.g., /n8n:create-pr)
    Cursor->>Project: Load skill implementation from plugin directory
    Project-->>Cursor: Skill instructions
    Cursor-->>User: Execute skill
    
    Note over Cursor,Project: Git Update Flow
    
    User->>Project: git pull (get new skills)
    Cursor->>Project: Auto-detect updated files (from registered path)
    Project-->>Cursor: Updated skills available without restart

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[codecov]

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