Expand description
Lightweight per-frame performance logger for rendering instrumentation.
Gated behind --features perf. When the feature is disabled, all types
become zero-size and all methods are no-ops that the compiler eliminates.
§Usage
cargo run --features perf -- --perf-log performance.log
# Writes JSON lines:
# {"run":"...","frame":1234,"ts_ms":1739599900793,"fn":"chat::render_msgs","ms":2.345,"n":42}