Emit deterministic synthetic bars on the scheduler (default: a 1s
setInterval). This actually streams, so feature detection
(if (feed.subscribeBars)) is honest. Pass a manual scheduler to drive it
by hand in tests, and opts.tickMs to change the cadence.
Optionalopts: BarSubscriptionOptions & { tickMs?: number }
Deterministic, in-memory data feed for tests and demos. No network. Generates a reproducible synthetic OHLC walk from a fixed seed so that pixel-diff and unit tests are stable across runs (no Math.random / Date.now).