feat(ci): add Android CI build and snapshot release workflow

[ppigazzini]

Run simulator tests and Android debug packaging in parallel on github_ci, pull requests, manual dispatch, and main. Resolve one authoritative C43 core revision per workflow run, sync that revision into both jobs, build the pinned xlsxio toolchain at run time, upload the debug APK with ABI and 16 KB packaging evidence, and let manual runs on main publish the synced-core snapshot release.

[Copilot]

Pull request overview

Adds a new GitHub Actions workflow to run Android-related CI on pushes (github_ci, main) and PRs, including simulator tests, debug APK packaging with artifact evidence, and automated prerelease publishing for main snapshots.

Changes:

• Introduces a parallelized workflow with a simulator test job (make test) and an Android debug build job (Gradle + NDK).
• Builds/restores a pinned xlsxio_xlsx2csv toolchain and syncs the upstream calculator core at workflow runtime.
• Uploads debug APK + verification outputs as an artifact, and publishes a main-branch snapshot prerelease from that artifact.

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[Copilot]

Pull request overview

Copilot reviewed 1 out of 1 changed files in this pull request and generated 8 comments.

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[paletochen]

Thanks a lot for this.
My project uses a bit of an unconventional setup with a private 'master' vault that automatically syncs to this public repository.
Because I use custom orchestration scripts to manage this sync, I’ve manually integrated your GitHub Actions and parallel build improvements into my workflow instead of doing a direct merge.
This keeps my internal tools running smoothly while giving the project the benefit of your faster build logic.

Really appreciate the contribution!