Require native Git runtime and bundle full manpages

- Remove the app fallback path when native Git is unavailable and show a startup blocker instead
- Fix native level setup for staged file counting and cherry-pick parity
- Improve manpage loading/search and bundle full Git documentation assets
- Integrate Git cross-compilation into AndroidProjectTooling.sh and remove debug AAB support

app/src/main/java/solutions/tretter/githugandroid/GitHugApp.kt

@@ -64,8 +64,13 @@ fun GitHugApp() {
     MaterialTheme(colorScheme = GitHugColorScheme) {
         val context = LocalContext.current
         val configuration = LocalConfiguration.current
-        val levels = remember { sampleLevels() }
         val runtime = remember(context) { GitRepositoryRuntime(context.applicationContext) }
+        if (!runtime.isNativeGitAvailable()) {
+            MissingNativeGitScreen(message = runtime.unavailableMessage())
+            return@MaterialTheme
+        }
+
+        val levels = remember { sampleLevels() }
         val paneLayoutStore = remember(context) { PaneLayoutStore(context.applicationContext) }
         val gameProgressStore = remember(context) { GameProgressStore(context.applicationContext) }
         val persistedPaneLayout by paneLayoutStore.layoutFlow.collectAsState(initial = defaultPaneLayout())
@@ -718,7 +723,7 @@ private fun HelpCalloutOverlay(
             } ?: Modifier
                 .align(Alignment.BottomStart)
                 .padding(start = 14.dp, bottom = 96.dp),
-            text = "Tap the prompt to enter a command.",
+            text = "Tap the prompt to enter a command or answer.",
             showHelpOnStart = showHelpOnStart,
             onShowHelpOnStartChange = onShowHelpOnStartChange,
             onOk = onOk,
@@ -836,6 +841,36 @@ private fun HelpBubble(
     }
 }
 
+@Composable
+private fun MissingNativeGitScreen(message: String) {
+    Surface(
+        modifier = Modifier
+            .fillMaxSize()
+            .background(AppBackground)
+            .padding(24.dp),
+        color = AppBackground,
+    ) {
+        Column(
+            modifier = Modifier.fillMaxSize(),
+            verticalArrangement = Arrangement.Center,
+            horizontalAlignment = Alignment.Start,
+        ) {
+            Text(
+                text = "Native Git unavailable",
+                color = TextPrimary,
+                fontWeight = FontWeight.Bold,
+                fontSize = 22.sp,
+            )
+            Text(
+                text = message,
+                modifier = Modifier.padding(top = 12.dp),
+                color = TextSecondary,
+                fontSize = 15.sp,
+            )
+        }
+    }
+}
+
 @Composable
 private fun SolvedCelebrationOverlay(title: String) {
     val transition = rememberInfiniteTransition(label = "solved-celebration")