feat: await support in browse js/eval + contributor mode v2 (#104)

* feat: support await in $B js and eval commands

Auto-wrap await expressions in async IIFE context so
$B js "await fetch(...)" works without SyntaxError.

- hasAwait() strips comments before detection
- js: expression wrapping (async()=>(expr))()
- eval: smart wrapping — single-line=expression, multi-line=block
- 6 new unit tests covering async, false-positive, and return semantics

* feat: redesign contributor mode — periodic reflection with 0-10 rating

Replace passive "report when things break" with active reflection:
- Rate gstack experience 0-10 at workflow step boundaries
- Historical calibration example (await bug) anchors the reporting bar
- "What would make this a 10" field focuses on actionable improvements
- Removed category lists in favor of judgment-based assessment

* test: add deterministic contributor mode preamble validation

40 new skill-validation tests (4 checks × 10 skills) verify:
- 0-10 rating scale present
- Calibration example present
- "What would make this a 10" field present
- Periodic reflection (not per-command)

Update existing E2E contributor eval for new report format.

* chore: bump version and changelog (v0.4.2)

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

* fix: improve contributor mode + qa-quick E2E reliability

Contributor mode:
- Add "do not truncate" directive to template — agent was stopping
  after "My rating" without completing Steps/Raw output/What would
  make this a 10 sections
- Restore assertions for Steps to reproduce and Date footer

QA quick:
- Make test server URL prominent: top of prompt, explicit "already
  running" and "do NOT discover ports" instructions
- Bump session timeout 180s→240s and test timeout 240s→300s
- Set B= at top of prompt (was buried in prose)

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

* fix: use flexible assertions for contributor mode E2E

Agent writes thorough reports with creative section names
("Repro Steps" vs "Steps to reproduce"). Match intent not formatting:
- /repro|steps to reproduce/ for reproduction steps
- /date.*2026/ for date footer presence

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

* docs: add E2E eval failure blame protocol

"Not related to our changes" is an extraordinary claim that requires
extraordinary proof. When evals fail during /ship:

1. Run the same eval on main — prove it fails there too
2. If it passes on main, it IS your change — trace the blame
3. If you can't verify, say "unverified" not "pre-existing"

Added to CLAUDE.md and as a comment in skill-e2e.test.ts.

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

* docs: update CONTRIBUTING.md and BROWSER.md for v0.4.2

CONTRIBUTING.md: update contributor mode description — now describes
periodic 0-10 reflection loop instead of passive friction detection.

BROWSER.md: add js/eval async documentation — await expressions are
auto-wrapped in async context, single-line eval returns values directly.

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

* fix: restore v0.4.2 changelog entries lost during cherry-pick conflict

The base branch detection entries from main were dropped when resolving
the CHANGELOG conflict — should have merged both sets, not replaced.

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

---------

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

scripts/gen-skill-docs.ts

@@ -123,12 +123,15 @@ Per-skill instructions may add additional formatting rules on top of this baseli
 
 ## Contributor Mode
 
-If \`_CONTRIB\` is \`true\`: you are in **contributor mode**. When you hit friction with **gstack itself** (not the user's app), file a field report. Think: "hey, I was trying to do X with gstack and it didn't work / was confusing / was annoying. Here's what happened."
+If \`_CONTRIB\` is \`true\`: you are in **contributor mode**. You're a gstack user who also helps make it better.
 
-**gstack issues:** browse command fails/wrong output, snapshot missing elements, skill instructions unclear or misleading, binary crash/hang, unhelpful error message, any rough edge or annoyance — even minor stuff.
-**NOT gstack issues:** user's app bugs, network errors to user's URL, auth failures on user's site.
+**At the end of each major workflow step** (not after every single command), reflect on the gstack tooling you used. Rate your experience 0 to 10. If it wasn't a 10, think about why. If there is an obvious, actionable bug OR an insightful, interesting thing that could have been done better by gstack code or skill markdown — file a field report. Maybe our contributor will help make us better!
 
-**To file:** write \`~/.gstack/contributor-logs/{slug}.md\` with this structure:
+**Calibration — this is the bar:** For example, \`$B js "await fetch(...)"\` used to fail with \`SyntaxError: await is only valid in async functions\` because gstack didn't wrap expressions in async context. Small, but the input was reasonable and gstack should have handled it — that's the kind of thing worth filing. Things less consequential than this, ignore.
+
+**NOT worth filing:** user's app bugs, network errors to user's URL, auth failures on user's site, user's own JS logic bugs.
+
+**To file:** write \`~/.gstack/contributor-logs/{slug}.md\` with **all sections below** (do not truncate — include every section through the Date/Version footer):
 
 \`\`\`
 # {Title}
@@ -137,20 +140,23 @@ Hey gstack team — ran into this while using /{skill-name}:
 
 **What I was trying to do:** {what the user/agent was attempting}
 **What happened instead:** {what actually happened}
-**How annoying (1-5):** {1=meh, 3=friction, 5=blocker}
+**My rating:** {0-10} — {one sentence on why it wasn't a 10}
 
 ## Steps to reproduce
 1. {step}
 
 ## Raw output
-(wrap any error messages or unexpected output in a markdown code block)
+\`\`\`
+{paste the actual error or unexpected output here}
+\`\`\`
+
+## What would make this a 10
+{one sentence: what gstack should have done differently}
 
 **Date:** {YYYY-MM-DD} | **Version:** {gstack version} | **Skill:** /{skill}
 \`\`\`
 
-Then run: \`mkdir -p ~/.gstack/contributor-logs && open ~/.gstack/contributor-logs/{slug}.md\`
-
-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}"`;
+Slug: lowercase, hyphens, max 60 chars (e.g. \`browse-js-no-await\`). 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}"`;
 }
 
 function generateBrowseSetup(): string {