ringbuffer-spsc

Removal of const generic for RingBuffer capacity

The RingBuffer no longer relies on a const generic parameter for its capacity.
The capacity is now stored directly in memory, making it significantly easier to embed both the RingbufferReader and RingbufferWriter inside user-defined structs without needing to propagate const generics through your type system.

This change improves ergonomics and simplifies integration into other data structures.

New initialization API

The RingBuffer is now constructed using the ringbuffer() function instead of the former RingBuffer::init() associated method.

let (mut reader, mut writer) = ringbuffer(capacity);

This provides a cleaner and more intuitive initialization API.

New reader methods: peek and peek_mut

RingbufferReader now supports:

• peek() – inspect data without consuming it
• peek_mut() – mutably inspect data without consuming it

These methods allow lookahead operations and in-place modifications while preserving the unread portion of the buffer.