fix note editor swallowing letter U by only intercepting Ctrl/Cmd shortcuts for non-letter keys

@@ -104,6 +104,10 @@104104 105105   function handleKeyDown(e: KeyboardEvent) {106106     const mod = e.metaKey || e.ctrlKey;107+    // Only intercept shortcuts for non-alphanumeric keys to avoid swallowing108+    // letter input. Letter keys (a–z, etc.) must always pass through freely.109+    const isLetterKey = e.key.length === 1;110+    if (isLetterKey) return;107111     if (mod && e.key === "b") { e.preventDefault(); exec("bold"); }108112     if (mod && e.key === "i") { e.preventDefault(); exec("italic"); }109113     if (mod && e.key === "u") { e.preventDefault(); exec("underline"); }