review(skills): convert-erlang-elm

## Skill Review

**Skill**: `convert-erlang-elm`
**Category**: convert

## Review Checklist

### Structure
- [ ] SKILL.md exists and has valid frontmatter
- [ ] SKILL.md is under 500 lines (use progressive disclosure if needed)
- [ ] Has Overview section with difficulty rating
- [ ] Has Quick Reference section
- [ ] Has type mapping table

### 8 Pillars Coverage
- [ ] Module System mapping (source → target)
- [ ] Error Handling mapping
- [ ] Concurrency mapping
- [ ] Metaprogramming mapping
- [ ] Zero/Default Values mapping
- [ ] Serialization mapping
- [ ] Build/Dependencies mapping
- [ ] Testing mapping

### Quality
- [ ] Description mentions both source and target languages
- [ ] Includes common gotchas section
- [ ] Links to source and target lang-*-dev skills
- [ ] Examples show before/after code

## Validation Command

```bash
just validate-skill components/skills/convert-erlang-elm
/validate-lang-conversion-skill convert-erlang-elm
```