feat(flutter-cursor-templates): add /debug, /verify, /explain skills and goldens.

Wire debug-issue, verify-change, and explain-code into the universal resolver with reasons, extend AGENTS.md slash list, cross-link build Phase 3 and Phase 6, refresh generator goldens for three stacks, and note cross-skill links in the build skill design spec.

Co-authored-by: Cursor <cursoragent@cursor.com>

flutter-cursor-templates/templates/skills/build/SKILL.md.tmpl

@@ -346,6 +346,7 @@ Follow Red → Green → Refactor strictly. Show actual terminal output at each
    flutter test test/features/[feature]/ --no-pub
    ```
    **Paste the actual output here before proceeding.**
+   If failures are unclear or non-deterministic after one iteration, use **`/debug`** with full pasted output before guessing fixes.
 
 ### Step 3b — Green: Implement
 
@@ -371,6 +372,8 @@ Follow Red → Green → Refactor strictly. Show actual terminal output at each
    **Paste the actual output here before proceeding.**
 3. Run tests once more to confirm still green.
 
+If output stays red or errors are ambiguous after two focused attempts, stop and use **`/debug`** with the full failing command and log before changing more code.
+
 ---
 
 ## Phase 4: Integration Test Generation
@@ -503,6 +506,8 @@ VERIFICATION REQUIRED — paste real output for each:
 ```
 
 If any check fails: invoke `superpowers:systematic-debugging` to diagnose before retrying.
+For noisy errors or weak reproduction, run **`/debug`** and fill the BugReport skeleton with logs before retrying.
+For small, isolated changes, **`/verify`** is enough to re-check tests and analyze without re-reading this whole skill.
 Do not proceed to Phase 7 until all four checks are green.
 
 ---