Add aarch64-linux-android build target with workflow_dispatch for Termux compatibility

[Copilot]

Adds aarch64-linux-android build target to produce Termux-compatible Codex CLI binaries for Android devices. Enables manual workflow triggering for testing without creating releases.

Changes

Workflow Trigger

• Added workflow_dispatch to allow manual builds
• Made tag-check, shell-tool-mcp, and release jobs conditional (tags only)
• Build job runs on both tag pushes and manual triggers

Android Build Configuration

• Target: aarch64-linux-android on ubuntu-24.04
• NDK 27.0.12077973 auto-installed via sdkmanager
• API level 21 (Android 5.0+) for maximum Termux device compatibility
• Environment variables configured:
  • CARGO_TARGET_AARCH64_LINUX_ANDROID_LINKER
  • CC_aarch64_linux_android → aarch64-linux-android21-clang
  • AR_aarch64_linux_android → llvm-ar

Conditional Exclusions

Android builds skip incompatible steps:

• CODEX_BWRAP_ENABLE_FFI=0 (no bubblewrap in Termux)
• Linux package dependencies (pkg-config, libcap)
• musl toolchain steps
• Sigstore code signing

Artifacts

• Binaries uploaded via actions/upload-artifact@v6
• Formats: .tar.gz and .zst
• Available in workflow run summary

Notes

• Codebase already handles Android via #[cfg(target_os = "android")]
• Clipboard support gracefully disabled (arboard incompatible)
• dotslash-config.json unchanged (mobile platform, not desktop tooling)
• Linker config via environment variables (no .cargo/config.toml changes)

Testing

Manually trigger workflow at Actions tab to build and download artifacts. Test in Termux:

pkg install wget zstd
tar -xzf codex-aarch64-linux-android.tar.gz
chmod +x codex-aarch64-linux-android
./codex-aarch64-linux-android --version

Original prompt

Please fully implement:

• Add aarch64-linux-android as a build target in .github/workflows/rust-release.yml.
• Enable workflow_dispatch so the build can be manually triggered.
• Ensure binaries are available as downloadable artifacts in the Action run summary (via actions/upload-artifact).
• Add steps to auto-install Android NDK and configure Rust cross-compilation for the new target (CC/AR variables, linker config—either via environment or .cargo/config.toml).
• Make all necessary conditional logic changes so Android build works correctly and existing musl/bwrap steps don't interfere.
• Update downstream config files if needed (dotslash-config.json, etc.)
• Ensure all tasks described in the detailed assessment above are complete; do not skip any discussed steps.

Do not use any previous PR; open a new PR, fully implementing everything above.

This pull request was created from Copilot chat.

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