CodeGraph CLI MCP Server

# codegraph-concurrent Concurrent, lock-free and wait-free data structures for CodeGraph. - WaitFreeSpscQueue: wait-free SPSC bounded ring buffer - LockFreeMpmcQueue: lock-free bounded MPMC (wrapper over crossbeam ArrayQueue) - LockFreeAdjacencyGraph: lock-free adjacency operations using ArcSwap + SkipMap ## Usage ```rust use codegraph_concurrent::spsc::WaitFreeSpscQueue; let (prod, cons) = WaitFreeSpscQueue::with_capacity(1024); prod.try_push(123).unwrap(); assert_eq!(cons.try_pop().unwrap(), 123); ``` Enable loom tests: ``` cargo test -p codegraph-concurrent --features loom ``` See `docs/memory_ordering.md` for ordering rationale.