Enhance getFileIconType to accept an extension parameter and cover all 13 FileAppearanceTypeEnum types using an O(1) Map lookup. Update all call sites to pass the API-provided extension for accurate icon display.
- Add types for sandbox file API (SandboxFileNode, SandboxFileDownloadTicket) - Add oRPC contracts for listFiles and downloadFile endpoints - Add TanStack Query hooks (useGetSandboxFiles, useDownloadSandboxFile) - Add useSandboxFilesTree hook with flat-to-tree conversion