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/sprint-plan/SKILL.md

@@ -142,6 +142,14 @@ Initialize each story from the sprint plan's task tables:
 For `update`: read the existing `sprint-status.yaml`, carry over statuses for
 stories that haven't changed, add new stories, remove dropped ones.
 
+### Scope Reminder
+
+After presenting the sprint plan, add:
+
+> **Scope check:** If this sprint includes stories added beyond the original epic scope, run `/scope-check [epic]` to detect scope creep before implementation begins.
+
+When reviewing stories during selection (step 3 above), note any stories that appear outside the original epic goals. If any are uncertain, flag them inline: "Are these stories within the original epic scope? If unsure, `/scope-check` can verify."
+
 ### Agent Consultation
 
 For comprehensive sprint planning, consider consulting: