feat: add skill rendering with <skill>name</skill> syntax

[JosXa]

Summary

Implements skill rendering in snippets as requested in #22.

Features

• New experimental flag: experimental.skillRendering (disabled by default)
• Two syntax options:
  • Block format: <skill>jira</skill>
  • Self-closing: <skill name="jira" />
• Skill loading from standard OpenCode paths:
  • Global: ~/.config/opencode/skill[s]/<name>/SKILL.md
  • Project: .opencode/skill[s]/<name>/SKILL.md
  • Claude compatibility: .claude/skills/<name>/SKILL.md
• Renders skill body verbatim (excludes YAML frontmatter)
• Processing order: skills → snippets → shell commands

Usage

1. Enable the feature in your config:

   {
     "experimental": {
       "skillRendering": true
     }
   }

2. Reference skills in your snippets or messages:

   Create a bug ticket. <skill>jira</skill>

Files Changed

• src/config.ts - Added experimental.skillRendering flag
• src/constants.ts - Added skill tag regex patterns
• src/skill-loader.ts - New file for loading skills from disk
• src/skill-renderer.ts - New file for expanding skill tags
• src/skill-renderer.test.ts - Comprehensive test suite
• index.ts - Integration of skill loading and rendering
• schema/config.schema.json - Updated config schema

Closes #22

[JosXa]

Yo opencode, please rebase. Another branch added experimental settings

[JosXa]

Done! Rebased onto main and resolved the conflict in index.ts where the session.idle handler from the inject tag feature was merged.

The merge conflict was straightforward - I combined both changes:

• The session.idle hook from main (for cleaning up injections)
• The skill rendering features from this PR

All tests pass ✓