fix(termux): add Android artifact support

[wallentx]

Summary

• add android-arm64 build target support for opencode artifacts
• build missing Android native dependencies from source in CI
• teach install/postinstall/publish paths about android-arm64

Notes

This PR is fork-local and exists to keep the Termux compatibility patch stack reviewable against upstream dev. Fork release/workflow automation stays on the dev branch.

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[github-actions]

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[Copilot]

Pull request overview

This PR adds Android (android-arm64) artifact support across the opencode build, packaging, install, and runtime-selection paths, including CI-side building of missing native deps and Android-specific ELF patching for Bun standalone binaries.

Changes:

• Add android-arm64 as a first-class build target and package it as a .tar.gz artifact.
• Extend install/postinstall/runtime binary selection to recognize the Android platform and pick the correct artifact.
• Add Android-native dependency handling (Parcel watcher binding + OpenTUI Android build + Bun ELF patching).

Reviewed changes

Copilot reviewed 10 out of 12 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
packages/opencode/script/publish.ts	Allows the wrapper package to be installable on Android via os: ["android", ...].
packages/opencode/script/postinstall.mjs	Adds Android platform mapping and selects only the Android base package name.
packages/opencode/script/patch-android-elf.ts	New script to patch Android AArch64 ELF relocation to fix Bun standalone payload pointer handling.
packages/opencode/script/opentui-android.ts	New script to build OpenTUI Android native library from source and patch the loader to support Android.
packages/opencode/script/build.ts	Adds android-arm64 target, --target= filtering, Android build conditions, and Android packaging format.
packages/opencode/bin/opencode	Adds Android platform mapping and Android package-name selection behavior.
packages/desktop/scripts/utils.ts	Adds Android Rust target ↔ opencode artifact mapping for sidecar workflows.
packages/core/src/flag/flag.ts	Disables FFF by default on Android (and Windows).
packages/core/src/filesystem/watcher.ts	Forces Android backend selection to inotify.
packages/core/package.json	Adds Android conditional import for #fff and includes @parcel/watcher-android-arm64.
install	Adds Termux/Android detection for linux/arm64, adjusts supported matrix, tar extraction, and temp dir selection.
bun.lock	Locks @parcel/watcher-android-arm64 version.

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