Gap closure: feedback loops, traceability, and new /content-audit skill

- NEW /content-audit skill: GDD-specified content vs implemented content gap
  report with COMPLETE/IN PROGRESS/EARLY/NOT STARTED per system
- balance-check: Fix & Verify Cycle phase (fix → re-verify → propagate-design-change)
- perf-profile: Scope & Timeline Decision phase for M/L effort optimizations
- playtest-report: Action Routing phase categorizes findings → design/balance/bugs/polish
- review-all-gdds: Phase 4 Cross-System Scenario Walkthrough (multi-system sequences)
- story-done: Test-Criterion Traceability (each AC mapped to a test, BLOCKING if >50% untested)
- code-review: ADR Compliance Check (ARCHITECTURAL VIOLATION / ADR DRIFT / MINOR DEVIATION)
- setup-engine: upgrade subcommand (pre-upgrade API scan, migration plan, VERSION.md update)
- story-readiness: Asset References Check (verifies referenced asset paths exist)
- validate-assets.sh: invalid JSON now exits 1 (blocking); naming issues exit 0 (warning)
- workflow-catalog.yaml + sprint-plan: /scope-check wired into production phase

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.claude/skills/balance-check/SKILL.md

@@ -72,3 +72,22 @@ When this skill is invoked:
 ### Values That Need Attention
 [Specific values with suggested adjustments and rationale]
 ```
+
+6. **Fix & Verify Cycle**
+
+   After presenting the report, ask:
+
+   > "Would you like to fix any of these balance issues now?"
+
+   If yes:
+   - Ask which issue to address first (refer to the Recommendations table by priority row)
+   - Guide the user to update the relevant data file in `assets/data/` or formula in `design/balance/`
+   - After each fix, offer to re-run the relevant balance checks for that system to verify the fix did not introduce new outliers or degenerate interactions
+   - If the fix changes a tuning knob that is defined in a GDD or referenced by an ADR, remind the user:
+     > "This value is defined in a design document. Run `/propagate-design-change [path]` on the affected GDD to find downstream impacts before committing."
+
+   If no:
+   - Summarize the open issues and suggest saving the report to `design/balance/balance-check-[system]-[date].md` for later.
+
+   End with:
+   > "Re-run `/balance-check` after fixes to verify."