app/ui: fix lint errors for unused vars, prefer-const, and empty catch (#15282)

app/ui/app/src/components/Message.tsx

@@ -536,7 +536,7 @@ function ToolCallDisplay({
     let args: Record<string, unknown> | null = null;
     try {
       args = JSON.parse(toolCall.function.arguments) as Record<string, unknown>;
-    } catch (e) {
+    } catch {
       args = null;
     }
     const query = args && typeof args.query === "string" ? args.query : "";
@@ -562,7 +562,7 @@ function ToolCallDisplay({
     let args: Record<string, unknown> | null = null;
     try {
       args = JSON.parse(toolCall.function.arguments) as Record<string, unknown>;
-    } catch (e) {
+    } catch {
       args = null;
     }
     const url = args && typeof args.url === "string" ? args.url : "";

app/ui/app/src/components/MessageList.tsx

@@ -73,7 +73,7 @@ export default function MessageList({
                     ? String(args.url).trim()
                     : "";
               if (candidate) lastQuery = candidate;
-            } catch {}
+            } catch { /* ignored */ }
           }
         }
       }

app/ui/app/src/components/ui/badge.tsx

@@ -65,7 +65,7 @@ export const BadgeButton = forwardRef(function BadgeButton(
     ),
   ref: React.ForwardedRef<HTMLElement>,
 ) {
-  let classes = clsx(
+  const classes = clsx(
     className,
     "group relative inline-flex rounded-md focus:not-data-focus:outline-hidden data-focus:outline-2 data-focus:outline-offset-2 data-focus:outline-blue-500",
   );

app/ui/app/src/components/ui/button.tsx

@@ -171,7 +171,7 @@ export const Button = forwardRef(function Button(
   { color, outline, plain, className, children, ...props }: ButtonProps,
   ref: React.ForwardedRef<HTMLElement>,
 ) {
-  let classes = clsx(
+  const classes = clsx(
     className,
     styles.base,
     outline