Mark fc-005 (usage tracking) as resolved

- Updated design document status to Implemented
- Marked all checklist items complete
- Updated fc-005 in future-considerations.json

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Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

plans/2026-01-01-usage-tracking-design.md

@@ -1,8 +1,8 @@
 # Model Usage & Cost Tracking Design
 
 **Date:** 2026-01-01
-**Status:** Approved
-**FC Reference:** fc-005
+**Status:** Implemented
+**FC Reference:** fc-005 (resolved)
 
 ## Overview
 
@@ -187,9 +187,9 @@ Tokens (est): ~125K input, ~42K output
 
 ## Implementation Checklist
 
-- [ ] Create `~/.claude/state/usage/config.json`
-- [ ] Create `~/.claude/skills/usage/SKILL.md`
-- [ ] Create `~/.claude/commands/usage.md`
-- [ ] Implement history parsing logic
-- [ ] Test with existing session data
-- [ ] Update fc-005 status to resolved
+- [x] Create `~/.claude/state/usage/config.json`
+- [x] Create `~/.claude/skills/usage/SKILL.md`
+- [x] Create `~/.claude/commands/usage.md`
+- [x] Implement history parsing logic
+- [x] Test with existing session data
+- [x] Update fc-005 status to resolved