fix(workflow): close parent UAT and debug artifacts after gap-closure phase (#580)

Add `close_parent_artifacts` step to execute-phase workflow that resolves
parent UAT gaps and debug sessions when a decimal/polish phase completes.

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

get-shit-done/workflows/execute-phase.md

@@ -226,6 +226,55 @@ After all waves:
 ```
 </step>
 
+<step name="close_parent_artifacts">
+**For decimal/polish phases only (X.Y pattern):** Close the feedback loop by resolving parent UAT and debug artifacts.
+
+**Skip if** phase number has no decimal (e.g., `3`, `04`) — only applies to gap-closure phases like `4.1`, `03.1`.
+
+**1. Detect decimal phase and derive parent:**
+```bash
+# Check if phase_number contains a decimal
+if [[ "$PHASE_NUMBER" == *.* ]]; then
+  PARENT_PHASE="${PHASE_NUMBER%%.*}"
+fi
+```
+
+**2. Find parent UAT file:**
+```bash
+find .planning/phases -path "*${PARENT_PHASE}*/*-UAT.md" -type f 2>/dev/null
+```
+
+**If no parent UAT found:** Skip this step (gap-closure may have been triggered by VERIFICATION.md instead).
+
+**3. Update UAT gap statuses:**
+
+Read the parent UAT file's `## Gaps` section. For each gap entry with `status: failed`:
+- Update to `status: resolved`
+
+**4. Update UAT frontmatter:**
+
+If all gaps now have `status: resolved`:
+- Update frontmatter `status: diagnosed` → `status: resolved`
+- Update frontmatter `updated:` timestamp
+
+**5. Resolve referenced debug sessions:**
+
+For each gap that has a `debug_session:` field:
+- Read the debug session file
+- Update frontmatter `status:` → `resolved`
+- Update frontmatter `updated:` timestamp
+- Move to resolved directory:
+```bash
+mkdir -p .planning/debug/resolved
+mv .planning/debug/{slug}.md .planning/debug/resolved/
+```
+
+**6. Commit updated artifacts:**
+```bash
+node ~/.claude/get-shit-done/bin/gsd-tools.js commit "docs(phase-${PARENT_PHASE}): resolve UAT gaps and debug sessions after ${PHASE_NUMBER} gap closure" --files .planning/phases/*${PARENT_PHASE}*/*-UAT.md .planning/debug/resolved/*.md
+```
+</step>
+
 <step name="verify_phase_goal">
 Verify phase achieved its GOAL, not just completed tasks.