Streaming a file's bytes through a channel

When to use

• A peer worker wants the bytes of a file without an inline copy in the trigger response.
• Streaming a large file into another channel (for example, uploading into a sandbox) without pinning a buffer in the orchestrator.
• Reading a binary that would not survive JSON encoding inline.

Notes

• Most LLM tool surfaces want bytes inlined into a tool result rather than a channel handle. For the harness web surface, the inline wrapper harness::fs::read_inline drives shell::fs::read, drains the channel, and returns the legacy { content: [{ text }], details: { size, truncated, bytes_read } } envelope. Use the wrapper from the browser; reach for shell::fs::read directly only when you actually want the streaming channel.
• When cfg.fs.max_read_bytes > 0 and the file's size exceeds it, the read is rejected before any bytes flow with S218 file size N exceeds max_read_bytes M. The default of 0 means no cap, which is unusual; operators typically pin a value.
• Same jail and denylist rules as shell::fs::ls.