fix: editor title textarea clips wrapped lines — add field-sizing + robust auto-resize

The textarea auto-resize was not reliably expanding for wrapped titles because
scrollHeight could be stale on the first read (e.g. during tab switches).
Added CSS field-sizing: content as the primary solution, plus requestAnimationFrame
and ResizeObserver fallbacks for older WebKit versions.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/components/Editor.css

@@ -336,6 +336,7 @@
   resize: none;
   overflow: hidden;
   font-family: inherit;
+  field-sizing: content;
 }
 
 .title-field__input::placeholder {