Feature Request: Plugin-bundled Skills Discovery

Summary

Allow plugins to bundle skills that are automatically discovered when the plugin is loaded.

Problem

Currently, OpenCode's skill discovery scans:

• .opencode/skills/ (project)
• ~/.config/opencode/skills/ (global)

But plugins at ~/.config/opencode/plugins/<name>/ cannot bundle skills that are auto-discovered. This forces plugin authors to either:

1. Ask users to manually copy skills to ~/.config/opencode/skills/
2. Implement a custom skill tool within the plugin (duplicating native functionality)
3. Deploy skills during plugin "install" (no standard mechanism)

Proposed Solution

Option A: Scan plugin directories for skills

Extend Skill.all() to also scan:

~/.config/opencode/plugins/*/skills/**/SKILL.md
~/.config/opencode/plugins/*/.opencode/skills/**/SKILL.md

Option B: Plugin hook for skill registration

Add a skills property to the Hooks interface:

interface Hooks {
  // ... existing
  skills?: Record<string, SkillDefinition>;
}

// Plugin usage
export default async function plugin() {
  return {
    tool: { ... },
    skills: {
      "my-skill": {
        name: "my-skill",
        description: "...",
        content: "# Instructions..."
      }
    }
  };
}

Option C: PluginInput includes skill registration

export default async function plugin({ registerSkill }: PluginInput) {
  registerSkill({
    name: "my-skill",
    description: "...",
    content: "..."
  });
  
  return { tool: {...} };
}

Use Case: NotebookLM Plugin

I'm building a NotebookLM plugin with 8 tools. Each tool has corresponding skill instructions. Currently I must:

• Deploy skills to ~/.config/opencode/skills/nlm-*/SKILL.md separately
• Skills are visible even when plugin is disabled
• No way to scope skills to plugin lifecycle

With this feature:

• Skills bundled with plugin
• Skills only available when plugin is active
• Single install = plugin + skills together

Benefits

1. Self-contained plugins - One package includes everything
2. Proper scoping - Skills tied to plugin lifecycle
3. Better UX - No manual skill deployment
4. Ecosystem growth - Easier to distribute complete plugin packages

Additional Context

• OpenCode version: Latest
• Plugin location: ~/.config/opencode/plugins/notebooklm/
• Reference: I've analyzed the skill discovery code in packages/opencode/src/skill/skill.ts