v0.8.68: Epic: official Termux / Android arm64 support

[Hmbown]

Summary

Users are asking for CodeWhale to run directly in Termux. Track official Android-native support for the CLI/TUI rather than relying on Linux arm64 release assets, which use the wrong ABI for Termux.

Follow-up context:

• Existing closed community signal: 已转译好termux版tui #1135
• Target platform: Termux on Android arm64 (aarch64-linux-android)
• Target release: v0.8.68

Scope

• Publish Android arm64 release binaries for codewhale, codew, and codewhale-tui.
• Bundle a Termux-friendly archive that installs into $PREFIX/bin.
• Make updater asset naming select Android assets explicitly.
• Document runtime limitations, especially sandbox/keyring behavior on Android.
• Add a repeatable Termux smoke checklist.

Child issues

• v0.8.68: Build and bundle Android arm64 release assets for Termux #4240
• v0.8.68: Teach updater to select Android assets on Termux #4241
• v0.8.68: Document Termux install and smoke-test workflow #4237
• v0.8.68: Make Android sandbox and secret-store behavior explicit #4238
• v0.8.68: Run Termux runtime QA for shell, PTY, config, and TUI startup #4242

Acceptance criteria

• codewhale-android-arm64, codew-android-arm64, and codewhale-tui-android-arm64 are built in release CI.
• A codewhale-android-arm64.tar.gz bundle is attached to releases with install.sh.
• codewhale update on Android looks for Android assets, not Linux assets.
• Docs include Termux install, setup, and known limitations.
• A maintainer can run a documented Termux smoke test and verify doctor, exec, and interactive TUI startup.