fix: editor title wraps to multiple lines instead of overflow hidden

Converted the title field from <input> to <textarea> with auto-resize
so long titles wrap naturally onto multiple lines. The textarea grows
to fit content (via scrollHeight) and shrinks back when text is
removed. Added resize:none and overflow:hidden in CSS to suppress
the drag handle and scrollbar.

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

src/components/Editor.css

@@ -333,6 +333,9 @@
   letter-spacing: var(--headings-h1-letter-spacing, -0.015em);
   color: var(--foreground);
   padding: 0;
+  resize: none;
+  overflow: hidden;
+  font-family: inherit;
 }
 
 .title-field__input::placeholder {