refactor(verify-work): consolidate plan-fix into plan-phase --gaps

Unify gap handling - whether discovered by code verification or user
testing, gaps feed into the same plan-phase --gaps workflow.

Changes:
- Delete commands/gsd/plan-fix.md (redundant)
- Update verify-work to route to plan-phase --gaps
- Update progress Route E to detect UAT gaps
- Change UAT.md "Issues" section to "Gaps" with YAML format
- Extend plan-phase --gaps to read from both VERIFICATION.md and UAT.md
- Update diagnose-issues to output gaps in YAML format
- Update all references (debug, templates, workflows)

One path: gap discovered → diagnosed → plan-phase --gaps → fixed

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

get-shit-done/workflows/debug.md

@@ -213,7 +213,7 @@ Reply with A or B (or describe alternative)
 - Diagnose but don't fix
 - Stop after confirming root cause
 - Skip `fix_and_verify` step
-- Return root cause to caller (for plan-fix to handle)
+- Return root cause to caller (for plan-phase --gaps to handle)
 
 **Default mode (no flags):**
 - Interactive debugging with user
@@ -544,7 +544,7 @@ If unable to determine root cause after thorough investigation:
 **Debug Session:** {path to debug file}
 ```
 
-**Do NOT proceed to fix_and_verify.** The fix will be planned by /gsd:plan-fix using this diagnosis.
+**Do NOT proceed to fix_and_verify.** The fix will be planned by /gsd:plan-phase --gaps using this diagnosis.
 </step>
 
 <step name="fix_and_verify">