refactor: reorganize template write paths + add frontmatter + manifest

All skill templates now write artifacts to subdirectories under
$PROJECTS_DIR/$SLUG/ (reviews/, plans/, reports/). Adds YAML
frontmatter to markdown artifacts and manifest-append calls.

Templates updated:
- plan-eng-review: plans/ + reviews/
- plan-ceo-review: plans/ceo/ + reviews/
- plan-design-review: reviews/
- ship: reviews/
- design-review: reports/
- qa: reports/
- qa-only: reports/
- review/greptile-triage: uses gstack-slug instead of remote-slug

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

plan-eng-review/SKILL.md.tmpl

@@ -111,16 +111,23 @@ For LLM/prompt changes: check the "Prompt/LLM changes" file patterns listed in C
 
 After producing the test diagram, write a test plan artifact to the project directory so `/qa` and `/qa-only` can consume it as primary test input (replacing the lossy git-diff heuristic):
 
+{{ARTIFACT_SETUP}}
+
 ```bash
-eval $(~/.claude/skills/gstack/bin/gstack-slug 2>/dev/null)
-USER=$(whoami)
-DATETIME=$(date +%Y%m%d-%H%M%S)
-mkdir -p ~/.gstack/projects/$SLUG
+mkdir -p $PROJECTS_DIR/$SLUG/plans
+FILE="$PROJECTS_DIR/$SLUG/plans/$DATE-$BRANCH-test-plan.md"
+[ -f "$FILE" ] && FILE="$PROJECTS_DIR/$SLUG/plans/$DATE-$(date +%H%M)-$BRANCH-test-plan.md"
 ```
 
-Write to `~/.gstack/projects/{slug}/{user}-{branch}-test-plan-{datetime}.md`:
+Write to the file path resolved above with this content (include the YAML frontmatter):
 
 ```markdown
+---
+type: test-plan
+branch: {branch}
+date: {YYYY-MM-DD}
+skill: plan-eng-review
+---
 # Test Plan
 Generated by /plan-eng-review on {date}
 Branch: {branch}
@@ -141,6 +148,11 @@ Repo: {owner/repo}
 
 This file is consumed by `/qa` and `/qa-only` as primary test input. Include only the information that helps a QA tester know **what to test and where** — not implementation details.
 
+After writing the test plan, register it in the manifest:
+```bash
+~/.claude/skills/gstack/bin/gstack-manifest-append test-plan "plans/$(basename "$FILE")" plan-eng-review "$BRANCH"
+```
+
 ### 4. Performance review
 Evaluate:
 * N+1 queries and database access patterns.
@@ -222,8 +234,8 @@ After producing the Completion Summary above, persist the review result:
 
 ```bash
 eval $(~/.claude/skills/gstack/bin/gstack-slug 2>/dev/null)
-mkdir -p ~/.gstack/projects/$SLUG
-echo '{"skill":"plan-eng-review","timestamp":"TIMESTAMP","status":"STATUS","unresolved":N,"critical_gaps":N,"mode":"MODE"}' >> ~/.gstack/projects/$SLUG/$BRANCH-reviews.jsonl
+mkdir -p $PROJECTS_DIR/$SLUG/reviews
+echo '{"skill":"plan-eng-review","timestamp":"TIMESTAMP","status":"STATUS","unresolved":N,"critical_gaps":N,"mode":"MODE"}' >> $PROJECTS_DIR/$SLUG/reviews/$BRANCH.jsonl
 ```
 
 Substitute values from the Completion Summary: