Function println_fmt 

pub fn println_fmt(ctx: &ServiceContext, args: Arguments<'_>)

Write a formatted line.

Formatting is bounded and allocates nothing: it renders through a fixed stack buffer (CLAUDE.md §26.6.1 is explicit that format_args! is the sanctioned bounded tool, and that hand-rolling digit formatting to avoid a heap it never touches is the mistake). Output longer than the buffer is written in pieces, never cut off.

io::println_fmt(ctx, format_args!("read {} bytes from {}", n, path));

Authority: log_write.