refactor(dashboard,desktop,engine): remove unused imports, props, and locals

Clears the remaining no-unused-vars warnings across the dashboard app and
server, desktop main, and engine sources. Dead React state destructures are
collapsed to setter-only, unused props are underscore-prefixed to preserve
API shape, and unreferenced catch bindings are dropped. No behaviour change.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

packages/dashboard/app/components/DevServerView.tsx

@@ -80,8 +80,6 @@ function truncateCommand(command: string): string {
 export function DevServerView({ addToast, projectId }: DevServerViewProps) {
   const {
     session,
-    sessions,
-    logs,
     detectedCommands,
     previewUrl,
     isLoading,
@@ -294,7 +292,6 @@ export function DevServerView({ addToast, projectId }: DevServerViewProps) {
     }
 
     const fallbackCwd = normalizeSourceToCwd(selectedSource) ?? ".";
-    const scriptName = selectedCandidate?.scriptName ?? selectedScript ?? "custom";
     const cwd = selectedCandidate?.cwd ?? fallbackCwd;
 
     void runAction(