fix(android): unbreak build from #8754 + gate Kotlin compile on PRs

[myleshorton]

Why

main's Android app does not compile. #8754 (Android sideload auto-updates) added a bare success(status) call in MethodHandler.onMethodCall's InstallSideloadUpdate branch:

scope.launch {
    try {
        val status = AndroidSideloadInstaller.install(MainActivity.instance, update)
        withContext(Dispatchers.Main) {
            success(status)        // ← e: Unresolved reference 'success'
        }
    } ...
}

success(...) is not a helper method — every other call site is inside a result.runCatching { … } block, where the implicit receiver this is the MethodChannel.Result, so success(...) resolves to MethodChannel.Result.success() (the Flutter API). Inside this scope.launch { … withContext(Dispatchers.Main) { } } block there is no result receiver, so it doesn't resolve and the Kotlin compile fails.

Fix

One line — qualify it explicitly:

-                            success(status)
+                            result.success(status)

result.error(...) is already used in the same branch's catch, so result is in scope.

Why it shipped broken — and the gate

build-android.yml is workflow_call-only (invoked by the release flow) and never runs on PRs or pushes. PR CI is only Go CI / CodeQL, neither of which compiles app Kotlin. So this merged undetected.

This PR adds android-compile-check.yml: on PRs touching android/**, lantern-core/**, go.mod/go.sum, Makefile, or pubspec* (i.e. anything that can break Kotlin compilation, directly or via the gomobile AAR), it builds the debug APK — which compiles all app Kotlin. Debug-only, so it needs no keystore/APP_ENV secrets and skips the AAB/signing/upload. This PR's own run of the gate (it touches both Kotlin and the workflow) doubles as its validation.

Verification

Locally on this branch: fresh gomobile AAR + make android-debug → ✓ Built build/app/outputs/flutter-apk/app-debug.apk. Installed on an Android 11 / API 30 emulator, connected the VPN successfully (no crash, traffic routed).

Follow-up worth considering: android-compile-check runs on macos-26 to match the known-good build-android environment; a Linux runner would be cheaper for a per-PR gate if the gomobile Android build is verified to work there.

[Copilot]

Pull request overview

Fixes a Kotlin compilation break in the Android MethodChannel handler introduced in #8754, and adds a PR-time CI gate to ensure Android/Kotlin compilation is exercised whenever Android- or gomobile-related changes are proposed.

Changes:

• Qualify the MethodChannel result call in InstallSideloadUpdate to result.success(...) to restore Kotlin compilation.
• Add a new android-compile-check GitHub Actions workflow that runs on PRs touching Android/gomobile-affecting paths and builds the debug APK (compiling all app Kotlin).

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
android/app/src/main/kotlin/org/getlantern/lantern/handler/MethodHandler.kt	Fixes the unresolved success(...) call by explicitly using result.success(status) inside the coroutine context.
.github/workflows/android-compile-check.yml	Adds a PR-triggered debug APK build to gate Android/Kotlin compilation on relevant PR changes.

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