design(preview): remove text labels from device toggles to match reference

vibn-frontend/components/project/project-icon-rail.tsx

@@ -198,11 +198,10 @@ function PreviewDeviceToggles() {
           style={{
             display: "flex",
             alignItems: "center",
-            gap: 6,
-            padding: "4px 10px",
+            justifyContent: "center",
+            width: 32,
+            height: 26,
             borderRadius: 6,
-            fontSize: "0.75rem",
-            fontWeight: 500,
             border: "none",
             cursor: "pointer",
             transition: "all 0.15s",
@@ -211,20 +210,19 @@ function PreviewDeviceToggles() {
             boxShadow:
               deviceMode === "desktop" ? "0 1px 2px rgba(0,0,0,0.05)" : "none",
           }}
+          title="Desktop view"
         >
           <Monitor size={14} />
-          Desktop
         </button>
         <button
           onClick={() => setDeviceMode("mobile")}
           style={{
             display: "flex",
             alignItems: "center",
-            gap: 6,
-            padding: "4px 10px",
+            justifyContent: "center",
+            width: 32,
+            height: 26,
             borderRadius: 6,
-            fontSize: "0.75rem",
-            fontWeight: 500,
             border: "none",
             cursor: "pointer",
             transition: "all 0.15s",
@@ -233,9 +231,9 @@ function PreviewDeviceToggles() {
             boxShadow:
               deviceMode === "mobile" ? "0 1px 2px rgba(0,0,0,0.05)" : "none",
           }}
+          title="Mobile view"
         >
           <Smartphone size={14} />
-          Mobile
         </button>
       </div>
     </div>