v0.1.0-alpha.2

Added

• Bare React Native 0.86.2, 0.86.3 and 0.87.1, through vendored copies of React Native 0.88.0's SwiftPM scripts
  (vendor/rn-spm/), a rn-artifacts build step that downloads and, for 0.86, adapts the prebuilt artifacts, and an
  exact-version gate. 0.86.3 and 0.87.1 are verified on a physical iPhone (doctor, build, install over Wi‑Fi, Metro,
  Fast Refresh, and the library matrix in docs/libraries.md; reanimated/worklets only on 0.86.3); 0.86.2 is
  build-verified only.
• The patches step warns about persisted scaffold patches made for another React Native version (for example after
  moving from 0.86.3 to 0.87.1) and says which file to delete; it changes nothing on its own.

Changed

• An Expo project whose react-native is not 0.88.0 now stops at the patches step with a message to pin
  react-native to 0.88.0 (before, a cleanly applying patch only warned).
• Persisted scaffold patches that still carry the old expo-xtool-scaffold-revision marker are re-scaffolded once (the
  marker became rn-xtool-scaffold-revision in 0.1.0-alpha.1); patches with the current marker are kept.
• A React Native version rn-xtool does not support now gets one error naming the supported list (0.86.2, 0.86.3,
  0.87.1 and 0.88.0); 0.88 prereleases and 0.88.x other than 0.88.0 are refused.
• README and docs mark WSL2 as "should work, not tested yet" instead of supported.