Route interactive Git through native terminal sessions

Remove Kotlin interactive-add emulation and run patch add via the native Git runtime with PTY-backed session IO.

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

@@ -12,6 +12,7 @@ data class GitFile(
     val staged: Boolean = false,
     val tracked: Boolean = false,
     val deleted: Boolean = false,
+    val stagedContent: String? = null,
 )
 
 data class CommitNode(
@@ -21,11 +22,9 @@ data class CommitNode(
     val parentCount: Int = 0,
 )
 
-data class InteractiveAddSession(
-    val target: String? = null,
-    val awaitingUpdateSelection: Boolean = false,
-    val selectionPrompt: String = "Update>>",
-    val selectionAction: String = "update",
+data class NativeGitSession(
+    val id: Int,
+    val command: String,
 )
 
 data class RepoState(
@@ -45,7 +44,7 @@ data class RepoState(
     val pushedTags: Set<String> = emptySet(),
     val submodules: Map<String, String> = emptyMap(),
     val maintenanceActions: Set<String> = emptySet(),
-    val interactiveAddSession: InteractiveAddSession? = null,
+    val nativeGitSession: NativeGitSession? = null,
 )
 
 data class Level(