fix(ui): forward-dialog header, notification presets, syntax-highlight tokens

- N14 ForwardMessageDialog: add folds <Header> with title + close IconButton
  (was closeable only by clicking outside)
- N20 Notification presets: bare <button> with undefined --border-interactive-
  normal / --bg-surface-low vars -> folds <Button variant="Secondary" fill="Soft">
- N68 syntaxHighlight tokenStyle: use the theme-aware --prism-* variable family
  (keyword/selector/boolean/atrule/comment) instead of TDS-only --lt-accent-*
  vars with dark-only Monokai fallbacks; comment uses --prism-comment not opacity

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/app/features/room/message/ForwardMessageDialog.tsx

@@ -4,6 +4,10 @@ import {
   Avatar,
   Box,
   config,
+  Header,
+  Icon,
+  IconButton,
+  Icons,
   Input,
   Line,
   MenuItem,
@@ -134,14 +138,22 @@ export function ForwardMessageDialog({ mEvent, onClose }: Props) {
               ...modalStyle,
             }}
           >
-            <Box
-              direction="Column"
-              gap="200"
-              shrink="No"
-              style={{ padding: config.space.S400, paddingBottom: config.space.S200 }}
+            <Header
+              variant="Surface"
+              size="500"
+              style={{ padding: `0 ${config.space.S200} 0 ${config.space.S400}` }}
             >
-              <Text size="H5">Forward message</Text>
-              {!sentTo && (
+              <Box grow="Yes">
+                <Text as="h2" size="H4" truncate>
+                  Forward message
+                </Text>
+              </Box>
+              <IconButton size="300" onClick={onClose} radii="300" aria-label="Close">
+                <Icon src={Icons.Cross} />
+              </IconButton>
+            </Header>
+            {!sentTo && (
+              <Box shrink="No" style={{ padding: `${config.space.S200} ${config.space.S400}` }}>
                 <Input
                   variant="Background"
                   size="400"
@@ -151,8 +163,8 @@ export function ForwardMessageDialog({ mEvent, onClose }: Props) {
                   value={query}
                   onChange={(e: ChangeEvent<HTMLInputElement>) => setQuery(e.target.value)}
                 />
-              )}
-            </Box>
+              </Box>
+            )}
             <Line size="300" />
             {sentTo ? (
               <Box