feat: design doc lookup in /plan-eng-review + fix branch name sanitization

Step 0 now checks ~/.gstack/projects/ for /brainstorm design docs
(branch-filtered with fallback, reads Supersedes: for revision context).

Fix: branch names with '/' (e.g. garrytan/better-process) now get
sanitized via tr '/' '-' in test plan artifact filenames.

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

plan-eng-review/SKILL.md

@@ -73,6 +73,31 @@ Then run: `mkdir -p ~/.gstack/contributor-logs && open ~/.gstack/contributor-log
 
 Slug: lowercase, hyphens, max 60 chars (e.g. `browse-snapshot-ref-gap`). Skip if file already exists. Max 3 reports per session. File inline and continue — don't stop the workflow. Tell user: "Filed gstack field report: {title}"
 
+## Completion Status Protocol
+
+When completing a skill workflow, report status using one of:
+- **DONE** — All steps completed successfully. Evidence provided for each claim.
+- **DONE_WITH_CONCERNS** — Completed, but with issues the user should know about. List each concern.
+- **BLOCKED** — Cannot proceed. State what is blocking and what was tried.
+- **NEEDS_CONTEXT** — Missing information required to continue. State exactly what you need.
+
+### Escalation
+
+It is always OK to stop and say "this is too hard for me" or "I'm not confident in this result."
+
+Bad work is worse than no work. You will not be penalized for escalating.
+- If you have attempted a task 3 times without success, STOP and escalate.
+- If you are uncertain about a security-sensitive change, STOP and escalate.
+- If the scope of work exceeds what you can verify, STOP and escalate.
+
+Escalation format:
+```
+STATUS: BLOCKED | NEEDS_CONTEXT
+REASON: [1-2 sentences]
+ATTEMPTED: [what you tried]
+RECOMMENDATION: [what the user should do next]
+```
+
 # Plan Review Mode
 
 Review this plan thoroughly before making any code changes. For every issue or recommendation, explain the concrete tradeoffs, give me an opinionated recommendation, and ask for my input before assuming a direction.
@@ -95,6 +120,16 @@ If you are running low on context or the user asks you to compress: Step 0 > Tes
 
 ## BEFORE YOU START:
 
+### Design Doc Check
+```bash
+SLUG=$(~/.claude/skills/gstack/browse/bin/remote-slug 2>/dev/null || basename "$(git rev-parse --show-toplevel 2>/dev/null || pwd)")
+BRANCH=$(git rev-parse --abbrev-ref HEAD 2>/dev/null | tr '/' '-' || echo 'no-branch')
+DESIGN=$(ls -t ~/.gstack/projects/$SLUG/*-$BRANCH-design-*.md 2>/dev/null | head -1)
+[ -z "$DESIGN" ] && DESIGN=$(ls -t ~/.gstack/projects/$SLUG/*-design-*.md 2>/dev/null | head -1)
+[ -n "$DESIGN" ] && echo "Design doc found: $DESIGN" || echo "No design doc found"
+```
+If a design doc exists, read it. Use it as the source of truth for the problem statement, constraints, and chosen approach. If it has a `Supersedes:` field, note that this is a revised design — check the prior version for context on what changed and why.
+
 ### Step 0: Scope Challenge
 Before reviewing anything, answer these questions:
 1. **What existing code already partially or fully solves each sub-problem?** Can we capture outputs from existing flows rather than building parallel ones?
@@ -147,7 +182,7 @@ After producing the test diagram, write a test plan artifact to the project dire
 
 ```bash
 SLUG=$(git remote get-url origin 2>/dev/null | sed 's|.*[:/]\([^/]*/[^/]*\)\.git$|\1|;s|.*[:/]\([^/]*/[^/]*\)$|\1|' | tr '/' '-')
-BRANCH=$(git rev-parse --abbrev-ref HEAD)
+BRANCH=$(git rev-parse --abbrev-ref HEAD | tr '/' '-')
 USER=$(whoami)
 DATETIME=$(date +%Y%m%d-%H%M%S)
 mkdir -p ~/.gstack/projects/$SLUG

plan-eng-review/SKILL.md.tmpl

@@ -38,6 +38,16 @@ If you are running low on context or the user asks you to compress: Step 0 > Tes
 
 ## BEFORE YOU START:
 
+### Design Doc Check
+```bash
+SLUG=$(~/.claude/skills/gstack/browse/bin/remote-slug 2>/dev/null || basename "$(git rev-parse --show-toplevel 2>/dev/null || pwd)")
+BRANCH=$(git rev-parse --abbrev-ref HEAD 2>/dev/null | tr '/' '-' || echo 'no-branch')
+DESIGN=$(ls -t ~/.gstack/projects/$SLUG/*-$BRANCH-design-*.md 2>/dev/null | head -1)
+[ -z "$DESIGN" ] && DESIGN=$(ls -t ~/.gstack/projects/$SLUG/*-design-*.md 2>/dev/null | head -1)
+[ -n "$DESIGN" ] && echo "Design doc found: $DESIGN" || echo "No design doc found"
+```
+If a design doc exists, read it. Use it as the source of truth for the problem statement, constraints, and chosen approach. If it has a `Supersedes:` field, note that this is a revised design — check the prior version for context on what changed and why.
+
 ### Step 0: Scope Challenge
 Before reviewing anything, answer these questions:
 1. **What existing code already partially or fully solves each sub-problem?** Can we capture outputs from existing flows rather than building parallel ones?
@@ -90,7 +100,7 @@ After producing the test diagram, write a test plan artifact to the project dire
 
 ```bash
 SLUG=$(git remote get-url origin 2>/dev/null | sed 's|.*[:/]\([^/]*/[^/]*\)\.git$|\1|;s|.*[:/]\([^/]*/[^/]*\)$|\1|' | tr '/' '-')
-BRANCH=$(git rev-parse --abbrev-ref HEAD)
+BRANCH=$(git rev-parse --abbrev-ref HEAD | tr '/' '-')
 USER=$(whoami)
 DATETIME=$(date +%Y%m%d-%H%M%S)
 mkdir -p ~/.gstack/projects/$SLUG