Add docs/mobile-ota.md covering how OTA works here, the branch and channel
model, the appVersion runtime version policy and its store-build rule, the
eoas publish commands per channel, both rollback paths, the pending native
prebuild, and the exact placeholders the server deployment still has to fill.
Index it and cross-link it from the release guide.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
