Align tests with runtime sandbox and polish terminal help

- Run level solution scenarios through GitRepositoryRuntime with a real filesystem sandbox and git binary so evidence logs match app behavior.
- Materialize synthetic remotes as local bare repositories and configure upstream tracking for pull/push levels.
- Route mobile-hostile Git interactions through shared sandbox semantics for clone, patch add, interactive rebase, squash merge, submodule, stash, revert, and related flows.
- Relax affected level validators to inspect observable runtime state instead of fallback-only staged/index details.
- Show .git in ls output for native and fallback helper commands.
- Make tab completion resolve filenames and directories relative to the current working directory.
- Integrate help controls into the callout overlay and reposition the prompt callout above the terminal prompt.
- Add regression coverage for .git listing and subfolder completion.

app/src/test/java/solutions/tretter/githugandroid/GitSandboxEngineTest.kt

@@ -122,6 +122,31 @@ class GitSandboxEngineTest {
         assertTrue(".gitignore" in output)
     }
 
+    @Test
+    fun lsShowsGitDirectoryEntry() {
+        val repo = RepoState(initialized = true)
+
+        val (_, output) = GitSandboxEngine.execute(repo, "ls")
+
+        assertTrue(".git" in output)
+    }
+
+    @Test
+    fun fileCompletionUsesCurrentDirectory() {
+        val repo = RepoState(
+            initialized = true,
+            currentDir = "src",
+            files = listOf(
+                GitFile("README"),
+                GitFile("src/main.kt"),
+                GitFile("src/model/User.kt"),
+            ),
+        )
+
+        assertEquals(listOf("main.kt", "model/User.kt"), fileCompletionCandidates(repo).sorted())
+        assertEquals(listOf("model/"), directoryCompletionCandidates(repo))
+    }
+
     @Test
     fun cdDotDotShortcutMovesToParentDirectory() {
         val repo = RepoState(initialized = true, currentDir = "src/main")