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>

BROWSER.md

@@ -127,6 +127,18 @@ The `console`, `network`, and `dialog` commands read from the in-memory buffers,
 
 Dialogs (alert, confirm, prompt) are auto-accepted by default to prevent browser lockup. The `dialog-accept` and `dialog-dismiss` commands control this behavior. For prompts, `dialog-accept <text>` provides the response text. All dialogs are logged to the dialog buffer with type, message, and action taken.
 
+### JavaScript execution (`js` and `eval`)
+
+`js` runs a single expression, `eval` runs a JS file. Both support `await` — expressions containing `await` are automatically wrapped in an async context:
+
+```bash
+$B js "await fetch('/api/data').then(r => r.json())"  # works
+$B js "document.title"                                  # also works (no wrapping needed)
+$B eval my-script.js                                    # file with await works too
+```
+
+For `eval` files, single-line files return the expression value directly. Multi-line files need explicit `return` when using `await`. Comments containing "await" don't trigger wrapping.
+
 ### Multi-workspace support
 
 Each workspace gets its own isolated browser instance with its own Chromium process, tabs, cookies, and logs. State is stored in `.gstack/` inside the project root (detected via `git rev-parse --show-toplevel`).