export interface StorageFileHint {
    sha256: string;
}
export interface StorageBackend {
    isSupported(): boolean;
    /**
     * Read a file from storage by key.
     * @returns Blob, or null if the key does not exist
     */
    read(key: string, hint?: StorageFileHint): Promise<Blob | null>;
    /**
     * Write a ReadableStream to storage under the given key.
     * Overwrites any existing content for that key.
     */
    write(key: string, stream: ReadableStream, hint?: StorageFileHint): Promise<void>;
    /**
     * Get the stored size of a file in bytes.
     * @returns number of bytes, or -1 if the key does not exist
     */
    getSize(key: string, hint?: StorageFileHint): Promise<number>;
    /**
     * List all keys currently in storage.
     * Includes metadata keys - callers are responsible for filtering.
     */
    list(): Promise<Array<{
        key: string;
        size: number;
    }>>;
    /**
     * Delete a single entry by key. No-op if the key does not exist.
     */
    delete(key: string): Promise<void>;
}