Harden Blocks Suite 0.5 release validation

[drewmt]

What changed

• Added standalone GitHub Actions coverage for static quality, deterministic builds, release ZIP installation, Plugin Check, WordPress/PHP compatibility, and classic/block themes.
• Added a committed lockfile so the public repository installs reproducibly with npm ci.
• Added keyboard, visible-focus, narrow reflow, generated RTL parity, and real Arabic RTL browser coverage.
• Kept browser-warning exceptions narrowly scoped to confirmed WordPress/WooCommerce messages.
• Extended the privacy-gated public exporter to ship only the required CI and test assets.
• Made generated bundles byte-for-byte stable across monorepo and standalone dependency layouts by using named Webpack module/chunk IDs.
• Upgraded official checkout/setup actions to v7 and removed duplicate branch/PR workflow runs.

Why

The public Blocks repository previously shipped the plugin and documentation but could not independently prove the same release gates as the monorepo. This change closes that gap without adding or changing frontend product features.

Validation

• Clean standalone public export: npm ci
• JavaScript, CSS, and PHP lint
• 24 JavaScript unit tests plus PHP regression tests
• Production build and 20 generated RTL stylesheet pairs
• Runtime dependency audit: 0 vulnerabilities
• Byte-for-byte clean rebuild from the standalone public checkout
• Full browser suite on Twenty Twenty-One and Twenty Twenty-Five: 7/7 on each
• Keyboard/focus/reflow browser test
• Real Arabic RTL anonymous frontend test
• Public allowlist/privacy export and screenshot documentation checks
• GitHub Actions run 31053196814: all 9 jobs green, including WordPress 6.9/current, PHP 8.3/8.4/8.5, release ZIP activation, and Plugin Check

Release status

This is release hardening only. No tag or public release should be created until this PR's CI is green and the release candidate has passed the planned staging-store gate.