fix(inputs): cap room-name / display-name length client-side (H10)

The room-name (settings + create-room) and display-name inputs had no client-side
length guard, so an over-long value only failed after a server round-trip. Add
maxLength={255} (matching the existing inline-rename cap in RoomNavItem; under
Synapse's 256 max_displayname_length). Also clamp the emoji-picker prepend in the
two room-name fields, since programmatic setState isn't constrained by the DOM
maxLength and could otherwise push past the cap.

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

src/app/features/common-settings/general/RoomProfile.tsx

@@ -122,7 +122,9 @@ export function RoomProfileEdit({
   const [emojiAnchor, setEmojiAnchor] = useState<RectCords>();
 
   const handleEmojiSelect = useCallback((unicode: string) => {
-    setNameValue((prev) => unicode + prev);
+    // Clamp to the same cap as the input's maxLength — programmatic setState isn't
+    // constrained by the DOM maxLength, so the picker could otherwise exceed it.
+    setNameValue((prev) => (unicode + prev).slice(0, 255));
     setEmojiAnchor(undefined);
   }, []);
 
@@ -309,6 +311,7 @@ export function RoomProfileEdit({
               onChange={(e: React.ChangeEvent<HTMLInputElement>) => setNameValue(e.target.value)}
               variant="Secondary"
               radii="300"
+              maxLength={255}
               readOnly={!canEditName || submitting}
               style={{ width: '100%' }}
             />

src/app/features/create-room/CreateRoom.tsx

@@ -102,7 +102,9 @@ export function CreateRoomForm({
   const [emojiAnchor, setEmojiAnchor] = useState<RectCords>();
 
   const handleEmojiSelect = useCallback((unicode: string) => {
-    setNameValue((prev) => unicode + prev);
+    // Clamp to the same cap as the input's maxLength — programmatic setState isn't
+    // constrained by the DOM maxLength, so the picker could otherwise exceed it.
+    setNameValue((prev) => (unicode + prev).slice(0, 255));
     setEmojiAnchor(undefined);
   }, []);
 
@@ -240,6 +242,7 @@ export function CreateRoomForm({
               disabled={disabled}
               value={nameValue}
               onChange={(e: React.ChangeEvent<HTMLInputElement>) => setNameValue(e.target.value)}
+              maxLength={255}
               style={{ width: '100%' }}
             />
           </Box>

src/app/features/settings/account/Profile.tsx

@@ -285,6 +285,7 @@ function ProfileDisplayName({ profile, userId }: ProfileProps) {
               onChange={handleChange}
               variant="Secondary"
               radii="300"
+              maxLength={255}
               style={{ paddingRight: config.space.S200 }}
               readOnly={changingDisplayName || disableSetDisplayname}
               after={