Improve upstream parity for level fixtures

- Add native per-level fixtures for complex histories, tags, branch graphs, rebases, resets, restores, stashes, and local remotes.
- Strengthen repository inspection so branch commit counts, remote-tracking branches, and detached tag checkouts reflect real Git state.
- Align Fetch, Pull, Push Branch, Branch At, and Rebase validators/tests with upstream-style repository state.
- Keep the prompt callout and native filesystem tab-completion fixes from the previous batch.

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

@@ -13,10 +13,13 @@ internal fun rebaseLevel(): Level = level(
     description = "We are using a git rebase workflow and the feature branch is ready to go into master. Let's rebase the feature branch onto our master branch.",
     hints = listOf("You want to research the `git rebase` command"),
     commandSuggestions = listOf("git checkout feature", "git rebase master"),
-    setup = { RepoState(initialized = true, headBranch = "feature", branches = mapOf("master" to 2, "feature" to 3)) },
-    validator = repoPredicate { repo -> repo.headBranch == "feature" && (repo.branches["feature"] ?: 0) >= (repo.branches["master"] ?: 0) },
+    setup = { RepoState(initialized = true, headBranch = "master", branches = mapOf("master" to 2, "feature" to 2)) },
+    validator = repoPredicate { repo ->
+        repo.headBranch == "feature" &&
+            repo.commits.take(3).map { it.message } == listOf("add feature", "add content", "init commit")
+    },
     testCases = listOf(
-        levelTestCase("rebase feature on master", "git rebase master"),
-        levelTestCase("checkout then rebase", "git checkout feature", "git rebase master"),
+        levelTestCase("checkout feature then rebase", "git checkout feature", "git rebase master"),
+        levelTestCase("rebase named branch", "git rebase master feature"),
     ),
 )