Fix Git editor reword workflow and UI coverage

- show Git editor file paths instead of the submitted git command
- surface follow-up commit message editors during interactive rebase reword
- add rename-commit UI tests for editor and amend-message solution paths
- add broader embedded level solution scenarios for alternate Git workflows

app/src/main/java/solutions/tretter/githugandroid/levels/BranchAtLevel.kt

@@ -28,5 +28,6 @@ internal fun branchAtLevel(): Level = level(
     testCases = listOf(
         levelTestCase("branch at previous commit", "git branch test_branch HEAD~1"),
         levelTestCase("branch at caret", "git branch test_branch HEAD^"),
+        levelTestCase("branch at explicit master parent", "git branch test_branch master^"),
     ),
 )