feat: handle non-letter characters in actor names with separator rows

Display spaces, hyphens and other non-letter characters as static cells
instead of input fields, and add separator rows in the grid for
non-alphabetic characters in the main actor's name.

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

assets/styles/app.css

@@ -75,6 +75,27 @@ body {
     color: var(--orange);
 }
 
+.letter-static {
+    width: 38px;
+    height: 38px;
+    text-align: center;
+    font-family: 'Inter', sans-serif;
+    font-size: 15px;
+    font-weight: 700;
+    text-transform: uppercase;
+    color: var(--text);
+    vertical-align: middle;
+}
+
+.separator-row td {
+    height: 12px;
+    padding: 0;
+}
+
+.separator-char {
+    height: 12px;
+}
+
 /* ── Popover ── */
 
 .popover-trigger {