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/review-all-gdds/SKILL.md

@@ -339,7 +339,90 @@ exploration.md: "You are a reckless adventurer — diving in without a plan"
 
 ---
 
-## Phase 4: Output the Review Report
+## Phase 4: Cross-System Scenario Walkthrough
+
+Walk through the game from the player's perspective to find problems that only
+appear at the interaction boundary between multiple systems — things static
+analysis of individual GDDs cannot surface.
+
+### 4a: Identify Key Multi-System Moments
+
+Scan all GDDs and identify the 3–5 most important player-facing moments where
+multiple systems activate simultaneously. Look specifically for:
+
+- **Combat + Economy overlap**: killing enemies that drop resources, spending
+  resources during combat, death/respawn interacting with economy state
+- **Progression + Difficulty overlap**: level-up triggering mid-fight, ability
+  unlocks changing combat viability, difficulty scaling at progression milestones
+- **Narrative + Gameplay overlap**: dialogue choices locking/unlocking mechanics,
+  story beats interrupting resource loops, quest completion triggering system
+  state changes
+- **3+ system chains**: any player action that triggers System A, which feeds
+  into System B, which triggers System C (these are highest-risk interaction paths)
+
+List each identified scenario with a one-line description before proceeding.
+
+### 4b: Walk Through Each Scenario
+
+For each scenario, step through the sequence explicitly:
+
+1. **Trigger** — what player action or game event starts this?
+2. **Activation order** — which systems activate, in what sequence?
+3. **Data flow** — what does each system output, and is that output a valid
+   input for the next system in the chain?
+4. **Player experience** — what does the player see, hear, or feel at each step?
+5. **Failure modes** — are there any of the following?
+   - **Race conditions**: two systems trying to modify the same state simultaneously
+   - **Feedback loops**: System A amplifies System B which re-amplifies System A
+     with no cap or dampener
+   - **Broken state transitions**: a system assumes a state that a previous
+     system may have changed (e.g., "player is alive" assumption after a combat
+     step that could have caused death)
+   - **Contradictory messaging**: player receives conflicting feedback from two
+     systems reacting to the same event (e.g., "success" sound + "failure" UI)
+   - **Compounding difficulty spikes**: two systems both scaling up at the same
+     progression point, multiplying the intended difficulty increase
+   - **Reward conflicts**: two systems both reacting to the same trigger with
+     rewards that together exceed the intended value (double-dipping)
+   - **Undefined behavior**: the GDDs don't specify what happens in this combined
+     state (neither system's rules cover it)
+
+```
+Example walkthrough:
+Scenario: Player kills elite enemy at level-up threshold during active quest
+
+Trigger: Player lands killing blow on elite enemy
+→ combat.md: awards kill XP (100 pts)
+→ progression.md: XP total crosses level threshold → triggers level-up
+  Output: new level, stat increases, ability unlock popup
+→ quest.md: kill-count criterion met → triggers quest completion event
+  Output: quest reward XP (500 pts), completion fanfare
+→ progression.md (again): quest XP added → triggers SECOND level-up in same frame
+  ⚠️  Data flow issue: quest.md awards XP without checking if a level-up
+  is already in progress. progression.md has no guard against concurrent
+  level-up events. Undefined behavior: does the player level up once or twice?
+  Does the ability popup fire twice? Does the second level use the updated or
+  pre-update stat baseline?
+```
+
+### 4c: Flag Scenario Issues
+
+For each problem found during the walkthrough, categorize severity:
+
+- **BLOCKER**: undefined behavior, broken state transition, or contradictory
+  player messaging — the experience is broken or incoherent in this scenario
+- **WARNING**: compounding spikes, feedback loops without caps, reward conflicts —
+  the experience works but produces unintended outcomes
+- **INFO**: minor ordering ambiguity or messaging overlap — worth noting but
+  unlikely to cause player-visible problems
+
+Add all findings to the output report under **"Cross-System Scenario Issues"**.
+Each finding must cite: the scenario name, the specific systems involved, the
+step where the issue occurs, and the nature of the failure mode.
+
+---
+
+## Phase 5: Output the Review Report
 
 ```
 ## Cross-GDD Review Report
@@ -373,6 +456,25 @@ Systems Covered: [list]
 
 ---
 
+### Cross-System Scenario Issues
+
+Scenarios walked: [N]
+[List scenario names]
+
+#### Blockers
+🔴 [Scenario name] — [Systems involved]
+[Step where failure occurs, nature of the failure mode, what must be resolved]
+
+#### Warnings
+⚠️  [Scenario name] — [Systems involved]
+[What the unintended outcome is, recommendation]
+
+#### Info
+ℹ️  [Scenario name] — [Systems involved]
+[Minor ordering ambiguity or note]
+
+---
+
 ### GDDs Flagged for Revision
 
 | GDD | Reason | Type | Priority |
@@ -395,7 +497,7 @@ FAIL: One or more blocking issues must be resolved before architecture begins.
 
 ---
 
-## Phase 5: Write Report and Flag GDDs
+## Phase 6: Write Report and Flag GDDs
 
 Ask: "May I write this review to `design/gdd/gdd-cross-review-[date].md`?"
 
@@ -410,7 +512,7 @@ Ask: "Should I update the systems index to mark these GDDs as needing revision?"
 
 ---
 
-## Phase 6: Handoff
+## Phase 7: Handoff
 
 After the report is written: