packaging: quarantine remaining legacy mobile app scripts from root package surface

[ToadAid]

• remove the remaining clearly legacy mobile app scripts from the root package surface:
  • android:assemble
  • android:install
  • android:test
  • ios:build
  • ios:gen
  • ios:open
• keep canonical Mirror-native scripts intact, including build:mirror, package:mirror-runtime, test:mirror, verify:mirror-runtime-*, and smoke:mirror
• update the focused package-boundary test to assert those legacy mobile scripts are absent
• preserve product code, workflows, build pipeline behavior, and service/sync/runtime behavior
• verification passed:
  • pnpm vitest run test/mirror-package-boundary.test.ts
  • pnpm exec oxfmt --check package.json test/mirror-package-boundary.test.ts

[ToadAid]

Closing this in favor of the rebased replacement branch.

This branch hit a package.json rebase conflict after main moved. I rebased the patch cleanly,
preserved the same packaging-only change, and pushed the resolved state to a replacement branch because
force-pushing this branch is blocked by repo rules.

Replacement branch:
mirror/packaging-quarantine-legacy-mobile-app-scripts-rebased