[EXPERIMENTAL] feat: #3608871 Ship a self-contained Playwright runtime under js/

EXPERIMENTAL

This is an experimental test MR that may or may not work in every environment. It ships a self-contained Playwright runtime as an opt-in js/ layout; if provisioning fails on a given host, the runner degrades gracefully and falls back to whatever Playwright install (if any) is already on PATH.

Summary

Issue: #3608871

The runtime browser tools in this module relied on Playwright being installed separately, with no self-contained way to ship/provision it with the module. This adds a js/ folder that:

• Owns a minimal js/package.json with a single playwright runtime dependency, kept separate from the root webship-js BDD test suite.
• Ships a runtime copy of the capture script (js/browser-capture.mjs).
• Excludes node_modules and downloaded browsers from git via js/.gitignore (too large for a module repo).

src/PlaywrightRunner.php changes:

• resolveScript() now prefers js/<name>, falling back to scripts/<name> for back-compatibility.
• ensureRuntime() provisions Playwright + headless Chromium into a writable browsers directory (PLAYWRIGHT_BROWSERS_PATH) on first use, when the bundled js/ layout is present but not yet installed.
• capture() runs with PLAYWRIGHT_BROWSERS_PATH pointed at that provisioned directory.

Local smoke test: capture used the js/ script, provisioned the browsers, and returned the Home page successfully.

AI-Generated: Yes (Used Claude Code).

Checkpoints

• File an issue about this project
• Addition/Change/Update/Fix to this project
• Testing to ensure no regression
• Automated unit/functional testing coverage
• Developer Documentation support on feature change/addition
• User Guide Documentation support on feature change/addition
• UX/UI designer responsibilities
• Accessibility and Readability
• Reviewed by a human
• Code review by maintainers
• Full testing and approval
• Credit contributors
• Review with the product owner
• Update Release Notes
• Release