feat(maestro): tui draft form gains a worktree section (#65)

Worktree on by default over a git repository with Enter/Space to spawn
in the checkout itself; base repo inferred from picked projects or a
guarded /api/gitroot probe for raw paths (a miss unticks, web parity);
new-branch name tracking the generated session name until touched;
Left/Right switches to picking an existing branch from GET /api/branches,
with held branches skipped and rendered dimmed beside their holder.
No cleanup option: cleanup is unconditional daemon-side (#56).

crates/maestro-tui/src/app.rs

@@ -767,6 +767,8 @@ mod tests {
         };
 
         draft.picked_cwd = Some(std::path::PathBuf::from("/srv/work"));
+        draft.base_repo = Some(std::path::PathBuf::from("/srv/work"));
+        draft.probed_cwd = Some(std::path::PathBuf::from("/srv/work"));
         draft.selected_preset = draft.presets.len() - 1; // custom
         app.handle_draft_input(&InputKey::Tab); // preset → custom command
         for c in "claude".chars() {
@@ -777,6 +779,9 @@ mod tests {
         for c in "crimson-otter".chars() {
             app.handle_draft_input(&InputKey::char(c));
         }
+        app.handle_draft_input(&InputKey::Tab); // → worktree toggle
+        app.handle_draft_input(&InputKey::Tab); // → branch mode
+        app.handle_draft_input(&InputKey::Tab); // → new-branch name
         app.handle_draft_input(&InputKey::Tab); // → submit
 
         match app.handle_draft_input(&InputKey::Enter).as_slice() {
@@ -800,7 +805,7 @@ mod tests {
         let mut app = make_app();
         app.dispatch(Action::NewDraftPane);
         // Walk to Submit without picking anything.
-        for _ in 0..3 {
+        for _ in 0..4 {
             app.handle_draft_input(&InputKey::Tab);
         }
         assert!(app.handle_draft_input(&InputKey::Enter).is_empty());