Mobile performance diagnostics

With the repository's Hermit environment active, run from mobile/:

flutter test --dart-define=BUZZ_RUN_BENCHMARKS=true test/benchmark/channel_live_burst_test.dart

The diagnostic is skipped by default. It does not use a relay, credentials, or community content.

The buffered-channel diagnostic sends synthetic events through the real RelaySessionNotifier event buffer and ChannelMessagesNotifier live callback. Only connection state and history responses are replaced. It measures one synchronous flush and a zero-delay timer queued just before that flush. The timer shows how long other event-loop work waits behind the consumer callbacks.

It varies retained history (50, 500, 2000 events) and live burst size (50, 200, 1000 events). Each case warms up twice before emitting four JSON measurement records in microseconds. Compare medians on the same host under similar load. No wall-clock threshold is asserted because debug/JIT compilation and host load make it unsuitable for a stable CI performance gate. Final event counts are asserted to ensure the measured work actually completes.

This is a bounded stress diagnostic, not a representative release benchmark. Retained history is modeled as one synthetic page instead of real pagination. It excludes widgets, media, network traffic, signature verification, and other subscriptions. It can identify synchronous consumer costs, but cannot establish that a measured burst occurred in a real community or predict release frame latency.