feat(maestro): move worktree choice behind advanced options

The worktree step ("+ new" plus the repository's existing worktrees) now
lives inside the collapsed "Advanced options" section in both the web form
and the TUI draft pane, so a plain spawn is command, project, name.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

web/src/spawnForm.ts

@@ -140,10 +140,6 @@ export function createSpawnForm(opts: SpawnFormOptions): SpawnFormHandle {
                placeholder="/home/user/project" inputmode="text" autocomplete="off" />
       </div>
     </div>
-    <div class="field wt-step" hidden>
-      <span class="field-label">Worktree</span>
-      <div class="picker wt-choices"></div>
-    </div>
     <div class="field">
       <span class="field-label">Name</span>
       <div class="name-row">
@@ -158,6 +154,10 @@ export function createSpawnForm(opts: SpawnFormOptions): SpawnFormHandle {
         <span class="wt-summary"></span>
       </button>
       <div class="wt-collapsible" hidden>
+        <div class="field wt-step" hidden>
+          <span class="field-label">Worktree</span>
+          <div class="picker wt-choices"></div>
+        </div>
         <label class="row-inline">
           <input type="checkbox" name="worktree_enabled" />
           Create git worktree