[Adityakk9031]

While inspecting ReadIOAdapter, noticed two issues with chunk reads:

1. read_enum was using slice!(..max_len), which takes an inclusive range (0..max_len) and ends up reading max_len + 1 bytes when there are enough bytes buffered. Switching this to slice!(0, max_len) ensures we don't exceed the requested length.
2. In read, .tap(&@blk) blows up with LocalJumpError (no block given) if the adapter was initialized without a block. Using .tap { @blk&.call(_1) } avoids yielding nil.

Added a couple of unit tests covering chunked reads and blockless initialization.