Module report_cache_stats 

Periodic-summary report-cache hit/miss instrumentation.

Replaces per-call tracing::debug! lines in CellServerCtx::report (which were firing thousands of times per scene load and dominated I/O).

The hot path increments per-report-id atomic counters via DashMap entry lookup; a single dedicated thread emits one summary log line every WINDOW_MS. Quiet windows emit nothing.

Functions

record_hit

record_hit_after_gate

record_miss

start_periodic_logger

Spawn the summary thread. Idempotent.