fix(webui): validate inferred file paths before preview (#4935)

webui/src/components/FilePreviewAvailabilityContext.tsx

@@ -0,0 +1,25 @@
+import { createContext, useContext, type ReactNode } from "react";
+
+export type FilePreviewAvailabilityResolver = (path: string) => Promise<boolean>;
+
+const FilePreviewAvailabilityContext = createContext<
+  FilePreviewAvailabilityResolver | undefined
+>(undefined);
+
+export function FilePreviewAvailabilityProvider({
+  children,
+  resolve,
+}: {
+  children: ReactNode;
+  resolve?: FilePreviewAvailabilityResolver;
+}) {
+  return (
+    <FilePreviewAvailabilityContext.Provider value={resolve}>
+      {children}
+    </FilePreviewAvailabilityContext.Provider>
+  );
+}
+
+export function useFilePreviewAvailabilityResolver() {
+  return useContext(FilePreviewAvailabilityContext);
+}