build(android): make release buildable and instrumented testing possible

Four gaps that made "ship it" and "test it on hardware" impossible.

RELEASE SIGNING. assembleRelease was silently producing
app-release-unsigned.apk because there was no signingConfigs block at all —
the failure mode where you only notice at install time. Credentials now
resolve from keystore.properties, then local.properties, then
WEBTERM_RELEASE_* env; nothing is created or committed, and
keystore.properties.example is the template.

The degradation is ENFORCED, not documented. The signingConfig is only
created when credentials actually resolve — an empty config is precisely what
makes AGP emit an unsigned artifact quietly — and a guard on packageRelease
throws with an actionable message, distinguishing "not configured" from
"credentials found but the keystore file is missing: <path>". It hooks the
PACKAGE task on purpose: R8 has already run and reported by then, so a
developer without a keystore still gets the full shrink result rather than an
early abort. Verified: minifyReleaseWithR8 completes, packageRelease fails
loudly, and no unsigned APK is written.

VERSIONING. Was still the scaffold 1 / "0.1.0". Now 1 / "0.1.0-alpha01",
where the suffix is a factual claim about device verification rather than
decoration: alpha means device QA is essentially unstarted, beta means the
A34/A35 checklist blocks pass on hardware, and plain 0.1.0 means the whole
checklist is ticked. versionCode stays 1 because no artifact has ever left
the build machine.

MINIFICATION. release had isMinifyEnabled = false and an empty rules file —
so nothing had ever exercised R8 on this app, and the first release build
would have been the experiment. Now minify + resource shrinking, with a
deliberately short rules file: the actual artifacts were checked, and
kotlinx.serialization, Tink, Hilt, FCM, OkHttp, Compose and CameraX all ship
their own consumer rules, so none are re-declared. The termux packages are
kept whole because the JitPack artifacts ship no rules and :terminal-view
binds to non-API internals — it writes the public TerminalView.mEmulator
field and calls TerminalRenderer.getFontWidth()/getFontLineSpacing(). Getting
that wrong yields a build that crashes only in production.
lintVitalRelease also passes now, the two pre-existing lint ERRORS having
been fixed earlier this session.

ANDROID TEST ENABLEMENT. :app had no androidTest source set and no
instrumentation runner, which is the mechanical reason A34/A35 have no code
at all. The runner (Hilt-aware) and dependencies are wired, and a
:macrobenchmark module exists. The tests themselves are a separate change.

Verified: ./gradlew test :app:assembleDebug :app:assembleDebugAndroidTest
:app:assembleBenchmark :macrobenchmark:assembleBenchmark
:app:lintVitalRelease koverVerify -> BUILD SUCCESSFUL; 901 JVM tests, 0
failures on a forced re-execution with test-results deleted and
--no-build-cache.

android/macrobenchmark/build.gradle.kts

@@ -0,0 +1,89 @@
+// ─────────────────────────────────────────────────────────────────────────────
+// :macrobenchmark (A35) — the macrobenchmark harness module.
+//
+// `com.android.test`, NOT `com.android.library`: macrobenchmark must drive the app
+// OUT of process (its own APK, its own process, UiAutomator across the boundary) so
+// that measured startup/frame timings are the real ones and not perturbed by the
+// test framework sharing the app's process.
+//
+// It instruments :app's `benchmark` variant — non-debuggable, R8'd and
+// resource-shrunk like release, but signed with the debug key so no release keystore
+// is needed (see app/build.gradle.kts → buildTypes.benchmark).
+//
+// This module currently has NO sources: the benchmark itself (pair → attach → type →
+// approve, plus a cold-start timing) is the next task's deliverable and belongs in
+// src/main/kotlin/. The module exists so that work is a matter of adding a file.
+//
+// Run (device/emulator required — `./gradlew :app:assembleDebug` style CI cannot):
+//   ./gradlew :macrobenchmark:connectedBenchmarkAndroidTest
+//
+// AGP 9 has built-in Kotlin → apply ONLY the android plugin (no kotlin.android).
+// The plugin id is applied BARE (no catalog alias / no version): the root build script
+// already puts AGP on the classpath via the android.library + android.application
+// aliases, and Gradle rejects a third versioned request for the same plugin artifact
+// ("already on the classpath with an unknown version"). The version is still pinned in
+// one place — `agp` in gradle/libs.versions.toml. Same pattern as :terminal-view.
+// ─────────────────────────────────────────────────────────────────────────────
+
+plugins {
+    id("com.android.test")
+}
+
+android {
+    namespace = "wang.yaojia.webterm.macrobenchmark"
+    compileSdk = 36
+
+    defaultConfig {
+        // Macrobenchmark itself needs API 23+; matching :app's 29 keeps the variant
+        // matrix honest (a benchmark on an SDK :app cannot run on is meaningless).
+        minSdk = 29
+        targetSdk = 35
+        testInstrumentationRunner = "androidx.test.runner.AndroidJUnitRunner"
+    }
+
+    compileOptions {
+        sourceCompatibility = JavaVersion.VERSION_17
+        targetCompatibility = JavaVersion.VERSION_17
+    }
+
+    buildTypes {
+        // The only variant this module is built in. `isDebuggable = true` applies to the
+        // TEST apk (never to :app) — required so the harness can be instrumented at all.
+        create("benchmark") {
+            isDebuggable = true
+            signingConfig = getByName("debug").signingConfig
+            // :app publishes debug/release/benchmark; libraries publish debug/release.
+            matchingFallbacks += listOf("release")
+        }
+    }
+
+    targetProjectPath = ":app"
+
+    // The harness runs in its OWN process and reaches the app only through UiAutomator /
+    // shell, never by linking against its classes. Without this, AGP's
+    // `checkTestedAppObfuscationBenchmark` refuses to build a non-minified test module
+    // against a minified app — a check that is correct for Espresso-style tests (which do
+    // link app symbols) and a false positive for macrobenchmark.
+    experimentalProperties["android.experimental.self-instrumenting"] = true
+}
+
+kotlin {
+    jvmToolchain(17)
+}
+
+// Only the `benchmark` variant is meaningful; disable the stock debug/release ones so
+// `./gradlew build` does not try to assemble a harness against a variant of :app that
+// does not exist.
+androidComponents {
+    beforeVariants { variant ->
+        variant.enable = variant.buildType == "benchmark"
+    }
+}
+
+dependencies {
+    // A `com.android.test` module's `main` source set IS its test code — deps go in
+    // implementation, not androidTestImplementation.
+    implementation(libs.androidx.test.ext.junit)
+    implementation(libs.androidx.test.uiautomator)
+    implementation(libs.androidx.benchmark.macro.junit4)
+}