PageScene: commit panel transform session on mouseup / Enter / Ctrl+Z

Follow-up to 72071c0066. The session-based panel transform recording
fixed pollution but introduced a new bug: while editing the same
object's panel without changing selection, the session never
committed, so Ctrl+Z fell through to the most recent prior entry —
typically the CreateAction for the shape, which deleted it on undo.

Add three document-level commit triggers covering the natural editing
boundaries the user expects:

- mouseup (any document-level mouseup): catches the end of an
  InputVector numeric-scrub drag and any click that moves focus
  elsewhere after typing.
- Enter key: explicit "done editing" commit even when the input
  retains focus.
- Ctrl+Z / Ctrl+Y (capture phase): flushes the pending session before
  the engine's keymap handler runs undo/redo, so the pending edit is
  what gets reverted instead of the prior entry.

Capture phase on the keydown listener is load-bearing: keymap.ts
attaches its handler in bubble phase via useViewportKeyboard. Capture
fires first, so the session commits before keymap dispatches.

mouseup commit is a no-op when no session is open, so attaching it
to document doesn't cost anything for unrelated clicks.

Color session is unchanged (focus/blur boundaries on the color
input still work and don't have this issue).

frontend/apps/artcraft/app/src/pages/PageScene/comps/ControlPanelSceneObject/ControlPanelSceneObject.tsx

@@ -172,6 +172,40 @@ export const ControlPanelSceneObject = () => {
     return () => commitPanelTransform();
   }, []);
 
+  // Document-level commit triggers for the transform session. These
+  // are the natural "end of edit gesture" signals — without them, a
+  // pending session sits open during same-uuid editing and Ctrl+Z
+  // falls through to a prior entry (often the CreateAction that
+  // added the shape, so the shape disappears on undo).
+  //
+  // - mouseup: end of an InputVector numeric-scrub drag, OR a click
+  //   that moves focus away after typing.
+  // - Enter: explicit "I'm done" without losing focus.
+  // - Ctrl+Z / Ctrl+Y / Ctrl+Shift+Z (capture phase): flush before the
+  //   engine's keymap handler runs the undo, so the pending entry is
+  //   the one being reverted.
+  useEffect(() => {
+    const flush = () => {
+      transformSessionRef.current?.commit();
+      transformSessionRef.current = null;
+    };
+    const onKeyDown = (e: KeyboardEvent) => {
+      if (e.key === "Enter") flush();
+      if (
+        (e.ctrlKey || e.metaKey) &&
+        (e.code === "KeyZ" || e.code === "KeyY")
+      ) {
+        flush();
+      }
+    };
+    document.addEventListener("mouseup", flush);
+    document.addEventListener("keydown", onKeyDown, true);
+    return () => {
+      document.removeEventListener("mouseup", flush);
+      document.removeEventListener("keydown", onKeyDown, true);
+    };
+  }, []);
+
   if (!currentSceneObject) {
     return null;
   }