Module ring_buffer 

Fixed-size ring buffer for streaming range bars (Issue #96 Task #9)

Replaces unbounded Vec with circular buffer to prevent OOM in long-running sidecars. When full, drops old bars gracefully instead of blocking producers.

Design:

• Fixed capacity (default 10K bars = 5MB)
• O(1) push/pop operations
• Thread-safe via parking_lot::Mutex (Issue #89)
• Metrics for backpressure, dropped bars, max depth

Structs

ConcurrentRingBuffer

Thread-safe wrapper for RingBuffer

RingBuffer

Fixed-size ring buffer with metrics

RingBufferMetrics

Metrics for ring buffer operations

RingBufferSlot

A single slot in the ring buffer