Migrate from Claude Code to OpenCode structure

- Move legacy content to legacy/ folder (old, old2, docs, learnings, scripts)
- Create new .opencode/ structure with skills/, tools/, agents/ folders
- Update Makefile to symlink to ~/.config/opencode/ instead of ~/.claude/
- Update Makefile to manage skills, tools, and agents (remove settings.json)
- Simplify install/uninstall (no backup logic)
- Add README.md documenting the new structure
- Keep settings.json as historical reference

legacy/old/skills/backlog-grooming/SKILL.md

@@ -0,0 +1,100 @@
+---
+name: backlog-grooming
+model: haiku
+description: Review and improve existing issues for clarity and actionability. Use when grooming the backlog, reviewing issue quality, cleaning up stale issues, or when the user wants to improve existing issues.
+user-invocable: false
+---
+
+# Backlog Grooming
+
+How to review and improve existing issues.
+
+## Grooming Checklist
+
+For each issue, verify:
+
+### 1. Title Clarity
+- [ ] Starts with action verb
+- [ ] Specific and descriptive
+- [ ] Understandable without reading description
+
+### 2. Description Quality
+- [ ] Has clear summary
+- [ ] Explains the "why"
+- [ ] Provides enough context
+
+### 3. Acceptance Criteria
+- [ ] Criteria exist
+- [ ] Each criterion is testable
+- [ ] Criteria are specific (not vague)
+- [ ] Complete set (nothing missing)
+
+### 4. Scope
+- [ ] Not too broad (can complete in reasonable time)
+- [ ] Not too narrow (meaningful unit of work)
+- [ ] Clear boundaries (what's included/excluded)
+
+### 5. Dependencies
+- [ ] Dependencies identified in description
+- [ ] Dependencies formally linked (`tea issues deps list <number>`)
+- [ ] No circular dependencies
+- [ ] Blocking issues are tracked
+
+To check/fix dependencies:
+```bash
+tea issues deps list <number>           # View current dependencies
+tea issues deps add <issue> <blocker>   # Add missing dependency
+tea issues deps remove <issue> <dep>    # Remove incorrect dependency
+```
+
+### 6. Labels
+- [ ] Type label (bug/feature/etc)
+- [ ] Priority if applicable
+- [ ] Component labels if applicable
+
+## Common Issues to Fix
+
+### Vague Titles
+- Bad: "Fix bug"
+- Good: "Fix login form validation on empty email"
+
+### Missing Acceptance Criteria
+Add specific, testable criteria based on the description.
+
+### Scope Creep
+If issue covers multiple features, split into separate issues.
+
+### Stale Issues
+- Close if no longer relevant
+- Update if context has changed
+- Add "needs-triage" label if unclear
+
+### Duplicate Issues
+- Close duplicate with reference to original
+- Merge relevant details into original
+
+## Grooming Workflow
+
+Use the gitea skill for issue operations.
+
+1. **Fetch open issues**
+2. **Review each issue** against checklist
+3. **Improve or flag** issues that need work
+4. **Update issue** with improvements
+5. **Add labels** as needed
+
+## Questions to Ask
+
+When grooming, consider:
+- "Could a developer start work on this today?"
+- "How will we know when this is done?"
+- "Is the scope clear?"
+- "Are dependencies explicit?"
+
+## Batch Grooming
+
+When grooming multiple issues:
+1. List all open issues
+2. Categorize by quality (ready, needs-work, stale)
+3. Focus on "needs-work" issues
+4. Present summary of changes made