Phase 3: /qa skill — systematic QA testing with health scores

New /qa skill for systematic web app QA testing. Three modes:
- full: 5-10 documented issues with screenshots and repro steps
- quick: 30-second smoke test with health score
- regression: compare against saved baseline

Includes issue taxonomy (7 categories, 4 severity levels), structured
report template, health score rubric (weighted across 7 categories),
framework detection guidance (Next.js, Rails, WordPress, SPA).

Also adds browse/bin/find-browse (DRY binary discovery using git
rev-parse), .gstack/ to .gitignore, and updated TODO roadmap.

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

qa/templates/qa-report-template.md

@@ -0,0 +1,79 @@
+# QA Report: {APP_NAME}
+
+| Field | Value |
+|-------|-------|
+| **Date** | {DATE} |
+| **URL** | {URL} |
+| **Scope** | {SCOPE or "Full app"} |
+| **Mode** | {full / quick / regression} |
+| **Duration** | {DURATION} |
+| **Pages visited** | {COUNT} |
+| **Screenshots** | {COUNT} |
+| **Framework** | {DETECTED or "Unknown"} |
+
+## Health Score: {SCORE}/100
+
+| Category | Score |
+|----------|-------|
+| Console | {0-100} |
+| Links | {0-100} |
+| Visual | {0-100} |
+| Functional | {0-100} |
+| UX | {0-100} |
+| Performance | {0-100} |
+| Accessibility | {0-100} |
+
+## Top 3 Things to Fix
+
+1. **{ISSUE-NNN}: {title}** — {one-line description}
+2. **{ISSUE-NNN}: {title}** — {one-line description}
+3. **{ISSUE-NNN}: {title}** — {one-line description}
+
+## Console Health
+
+| Error | Count | First seen |
+|-------|-------|------------|
+| {error message} | {N} | {URL} |
+
+## Summary
+
+| Severity | Count |
+|----------|-------|
+| Critical | 0 |
+| High | 0 |
+| Medium | 0 |
+| Low | 0 |
+| **Total** | **0** |
+
+## Issues
+
+### ISSUE-001: {Short title}
+
+| Field | Value |
+|-------|-------|
+| **Severity** | critical / high / medium / low |
+| **Category** | visual / functional / ux / content / performance / console / accessibility |
+| **URL** | {page URL} |
+
+**Description:** {What is wrong, expected vs actual.}
+
+**Repro Steps:**
+
+1. Navigate to {URL}
+   ![Step 1](screenshots/issue-001-step-1.png)
+2. {Action}
+   ![Step 2](screenshots/issue-001-step-2.png)
+3. **Observe:** {what goes wrong}
+   ![Result](screenshots/issue-001-result.png)
+
+---
+
+## Regression (if applicable)
+
+| Metric | Baseline | Current | Delta |
+|--------|----------|---------|-------|
+| Health score | {N} | {N} | {+/-N} |
+| Issues | {N} | {N} | {+/-N} |
+
+**Fixed since baseline:** {list}
+**New since baseline:** {list}