feat(studio): edit and style text in the preview (#3143)

* feat(studio): edit and style text in the preview

Double-press a text element in the canvas and the caret opens where you
pressed, in the element itself rather than in a panel. Select characters and
a small toolbar offers colour, bold, italic and underline, applied to
exactly those characters.

The toolbar lives in Studio's document rather than the composition's.
Putting it in the preview would inject Studio's chrome into the user's
composition, where a render would capture it and the composition's own
styling would inherit into it.

In a flex or grid container the rebuilt runs go inside one wrapper, so a
coloured word cannot reflow the element it sits in.

Also fixes the keyboard: the shortcut guards matched contenteditable=true
only, so playback shortcuts ate letters typed into the composition.

* refactor(studio): keep domEditingLayers under the size cap

The rich-text operation pushed this file past the 600-line gate. Same change
the branch made later, landed with the commit that caused it.

* test(studio): wrap selection changes in act

* fix(studio): restore rich text after failed save

* fix(studio): polish inline text editing

* fix(studio): harden inline text editing

packages/studio/src/player/lib/playbackShortcuts.ts

@@ -6,15 +6,13 @@
  * is active and the user is navigating caption segments).
  */
 
+import { isTypingTarget } from "../../utils/typingTarget";
+
 const PLAYBACK_FRAME_STEP_CODES = new Set(["ArrowLeft", "ArrowRight"]);
 
 const PLAYBACK_SHORTCUT_IGNORED_SELECTOR = [
-  "input",
-  "textarea",
-  "select",
   "button",
   "a[href]",
-  "[contenteditable='true']",
   "[role='button']",
   "[role='checkbox']",
   "[role='combobox']",
@@ -27,6 +25,9 @@ const PLAYBACK_SHORTCUT_IGNORED_SELECTOR = [
 ].join(",");
 
 export function shouldIgnorePlaybackShortcutTarget(target: EventTarget | null): boolean {
+  // Anything the user is typing into owns its keys outright, editable elements
+  // included: a letter claimed here never reaches the text.
+  if (isTypingTarget(target)) return true;
   if (!target || typeof target !== "object") return false;
   const candidate = target as { closest?: unknown };
   if (typeof candidate.closest !== "function") return false;