Aggregates a fine 4-field OHLC stream into period_minutes buckets (open=first,
high=max, low=min, close=last), emitting a completed bar ONLY on bucket rollover
(ctx.now() crossing into the next bucket) — C2: a bar is actionable only once
complete, partials are never emitted and the last partial bar is dropped (no EOF
flush). Four Barrier(0) f64 inputs, a 4-field f64 record output (the first
multi-field-output node in aura-std, mirroring the Ohlcv engine fixture). The bar
carries no timestamp; the engine stamps the close-instant. Build-step 6 of
milestone 'Strategy node vocabulary I'.
closes#89
Brummel
0e1eee61bd