Read a file and return its raw content for the requested window.
The content is returned unformatted: the Deep Agents middleware applies
line numbering, the empty-file reminder, and base64 multimodal handling
based on the encoding field. Blobs whose extension classifies as
non-text (image/audio/video/file), or whose bytes are not valid UTF-8,
are returned base64-encoded with encoding="base64".
Virtual path to the file.
Zero-based line offset to start reading from.
Maximum number of lines to return.
