fix(maestro): update stale worktree test for branch-collision suffixing

add_fails_when_branch_already_exists asserted the pre-#77 behavior:
that a branch collision errors outright. Since 49ab7e9, add_new
sidesteps a branch collision with a numeric suffix instead, so the
test was failing CI on main regardless of any given change.

Replaces it with a test asserting the actual (and intended) suffixing
behavior.

crates/maestro-daemon/tests/worktree.rs

@@ -405,13 +405,17 @@ fn run_git(dir: &std::path::Path, args: &[&str]) {
     );
 }
 
+/// `git worktree add -b` alone fails outright when the branch already exists,
+/// even with the target directory free — a random handle commonly collides
+/// with one an earlier, already-removed worktree left behind. `add_new`
+/// sidesteps it on the branch name itself instead of erroring (#77).
 #[test]
-fn add_fails_when_branch_already_exists() {
+fn add_new_suffixes_branch_name_on_branch_collision() {
     let repo_dir = TempDir::new().unwrap();
     let repo = repo_dir.path().to_path_buf();
     init_repo(&repo);
 
-    // pre-create the branch
+    // pre-create the branch, unused by any worktree.
     let status = Command::new("git")
         .arg("-C")
         .arg(&repo)
@@ -423,9 +427,17 @@ fn add_fails_when_branch_already_exists() {
     let wt_root = TempDir::new().unwrap();
     let mgr = WorktreeManager::new(Some(wt_root.path().to_path_buf()));
 
-    let err = mgr.add_new(&repo, "feat/dup").unwrap_err();
-    let msg = format!("{err}");
-    assert!(msg.contains("git exited"), "{msg}");
+    let path = mgr
+        .add_new(&repo, "feat/dup")
+        .expect("sidesteps the branch collision");
+    assert!(path.ends_with("feat/dup-2"), "{}", path.display());
+    assert!(path.exists());
+
+    // The pre-existing branch is untouched; the new worktree checked out the
+    // suffixed one instead of erroring or adopting `feat/dup`.
+    let branches = worktree_branches(&repo);
+    assert!(branches.contains(&"feat/dup-2".to_string()), "{branches:?}");
+    assert!(!branches.contains(&"feat/dup".to_string()), "{branches:?}");
 }
 
 /// The project picker lists linked worktrees as pickable rows, so `base_repo`