feat: QA restructure, browser ref staleness, eval efficiency metrics (v0.4.0) (#83)

* feat: browser ref staleness detection via async count() validation

resolveRef() now checks element count to detect stale refs after page
mutations (e.g. SPA navigation). RefEntry stores role+name metadata
for better diagnostics. 3 new snapshot tests for staleness detection.

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

* feat: qa-only skill, qa fix loop, plan-to-QA artifact flow

Add /qa-only (report-only, Edit tool blocked), restructure /qa with
find-fix-verify cycle, add {{QA_METHODOLOGY}} DRY placeholder for
shared methodology. /plan-eng-review now writes test-plan artifacts
to ~/.gstack/projects/<slug>/ for QA consumption.

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

* feat: eval efficiency metrics — turns, duration, commentary across all surfaces

Add generateCommentary() for natural-language delta interpretation,
per-test turns/duration in comparison and summary output, judgePassed
unit tests, 3 new E2E tests (qa-only, qa fix loop, plan artifact).

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

* chore: bump version and changelog (v0.4.0)

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

* docs: update ARCHITECTURE, BROWSER, CONTRIBUTING, README for v0.4.0

- ARCHITECTURE: add ref staleness detection section, update RefEntry type
- BROWSER: add ref staleness paragraph to snapshot system docs
- CONTRIBUTING: update eval tool descriptions with commentary feature
- README: fix missing qa-only in project-local uninstall command

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

* docs: add user-facing benefit descriptions to v0.4.0 changelog

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

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

README.md

@@ -2,7 +2,7 @@
 
 **gstack turns Claude Code from one generic assistant into a team of specialists you can summon on demand.**
 
-Eight opinionated workflow skills for [Claude Code](https://docs.anthropic.com/en/docs/claude-code). Plan review, code review, one-command shipping, browser automation, QA testing, and engineering retrospectives — all as slash commands.
+Nine opinionated workflow skills for [Claude Code](https://docs.anthropic.com/en/docs/claude-code). Plan review, code review, one-command shipping, browser automation, QA testing, and engineering retrospectives — all as slash commands.
 
 ### Without gstack
 
@@ -22,7 +22,8 @@ Eight opinionated workflow skills for [Claude Code](https://docs.anthropic.com/e
 | `/review` | Paranoid staff engineer | Find the bugs that pass CI but blow up in production. Triages Greptile review comments. |
 | `/ship` | Release engineer | Sync main, run tests, resolve Greptile reviews, push, open PR. For a ready branch, not for deciding what to build. |
 | `/browse` | QA engineer | Give the agent eyes. It logs in, clicks through your app, takes screenshots, catches breakage. Full QA pass in 60 seconds. |
-| `/qa` | QA lead | Systematic QA testing. On a feature branch, auto-analyzes your diff, identifies affected pages, and tests them. Also: full exploration, quick smoke test, regression mode. |
+| `/qa` | QA + fix engineer | Test app, find bugs, fix them with atomic commits, re-verify. Before/after health scores and ship-readiness summary. Three tiers: Quick, Standard, Exhaustive. |
+| `/qa-only` | QA reporter | Report-only QA testing. Same methodology as /qa but never fixes anything. Use when you want a pure bug report without code changes. |
 | `/setup-browser-cookies` | Session manager | Import cookies from your real browser (Comet, Chrome, Arc, Brave, Edge) into the headless session. Test authenticated pages without logging in manually. |
 | `/retro` | Engineering manager | Team-aware retro: your deep-dive + per-person praise and growth opportunities for every contributor. |
 
@@ -103,7 +104,7 @@ This is the setup I use. One person, ten parallel agents, each with the right co
 
 Open Claude Code and paste this. Claude will do the rest.
 
-> Install gstack: run `git clone https://github.com/garrytan/gstack.git ~/.claude/skills/gstack && cd ~/.claude/skills/gstack && ./setup` then add a "gstack" section to CLAUDE.md that says to use the /browse skill from gstack for all web browsing, never use mcp\_\_claude-in-chrome\_\_\* tools, and lists the available skills: /plan-ceo-review, /plan-eng-review, /review, /ship, /browse, /qa, /setup-browser-cookies, /retro. Then ask the user if they also want to add gstack to the current project so teammates get it.
+> Install gstack: run `git clone https://github.com/garrytan/gstack.git ~/.claude/skills/gstack && cd ~/.claude/skills/gstack && ./setup` then add a "gstack" section to CLAUDE.md that says to use the /browse skill from gstack for all web browsing, never use mcp\_\_claude-in-chrome\_\_\* tools, and lists the available skills: /plan-ceo-review, /plan-eng-review, /review, /ship, /browse, /qa, /qa-only, /setup-browser-cookies, /retro. Then ask the user if they also want to add gstack to the current project so teammates get it.
 
 ### Step 2: Add to your repo so teammates get it (optional)
 
@@ -613,7 +614,7 @@ Or set `auto_upgrade: true` in `~/.gstack/config.yaml` to upgrade automatically
 
 Paste this into Claude Code:
 
-> Uninstall gstack: remove the skill symlinks by running `for s in browse plan-ceo-review plan-eng-review review ship retro qa setup-browser-cookies; do rm -f ~/.claude/skills/$s; done` then run `rm -rf ~/.claude/skills/gstack` and remove the gstack section from CLAUDE.md. If this project also has gstack at .claude/skills/gstack, remove it by running `for s in browse plan-ceo-review plan-eng-review review ship retro qa setup-browser-cookies; do rm -f .claude/skills/$s; done && rm -rf .claude/skills/gstack` and remove the gstack section from the project CLAUDE.md too.
+> Uninstall gstack: remove the skill symlinks by running `for s in browse plan-ceo-review plan-eng-review review ship retro qa qa-only setup-browser-cookies; do rm -f ~/.claude/skills/$s; done` then run `rm -rf ~/.claude/skills/gstack` and remove the gstack section from CLAUDE.md. If this project also has gstack at .claude/skills/gstack, remove it by running `for s in browse plan-ceo-review plan-eng-review review ship retro qa qa-only setup-browser-cookies; do rm -f .claude/skills/$s; done && rm -rf .claude/skills/gstack` and remove the gstack section from the project CLAUDE.md too.
 
 ## Development