release.yml builds linux-x64/arm64 + win-x64 (cross) on free Linux runners and
macos-arm64/x64 on native Mac runners; packages per the wrapper contract
(juggler-gated so binaries are Playwright-drivable, issue-#14 symlink-safe via
cp -aL), validate_release.py gate, ad-hoc macOS codesign, DRAFT publish.
constants.py: arm64 + darwin ARCHIVE_NAME + BINARY_ENTRY_REL (Firefox.app).
download.py: macOS post-extract xattr quarantine strip.
BINARY_VERSION unchanged (firefox-8); the juggler-fixed firefox-9 is a separate
release cut + pin bump.
