feat(maestro): default structured view on for ACP agents

A Claude Code or Codex spawn now asks for the structured view unless the
operator says otherwise: the two spawn forms open with the box ticked and
`maestro spawn` takes `--terminal` to opt out. Once the operator works the
toggle, a command change no longer re-ticks it under them.

The support predicate moves to `maestro_protocol::display` so all three
clients gate on the same resolution.

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

web/src/spawnForm.ts

@@ -375,13 +375,23 @@ export function createSpawnForm(opts: SpawnFormOptions): SpawnFormHandle {
   // operator has already touched (#76).
   let commandTouched = false;
 
+  // Set once the operator works the checkbox themselves. Until then every
+  // command change re-derives the default (on for Claude Code and Codex, off
+  // for everything else); afterwards their choice outranks it, the same guard
+  // `commandTouched` gives the command field.
+  let structuredTouched = false;
+
   function updateStructuredAvailability(): void {
     const supported = supportsStructuredView(command);
     structuredWrap.hidden = !supported;
     if (!supported) structuredView.checked = false;
+    else if (!structuredTouched) structuredView.checked = true;
   }
 
-  structuredView.addEventListener("change", emit);
+  structuredView.addEventListener("change", () => {
+    structuredTouched = true;
+    emit();
+  });
 
   cmdRaw.addEventListener("input", () => {
     if (selectedPresetId === "custom" || presets.find((p) => p.id === selectedPresetId)?.command === "") {