Maps ctx.now() (epoch-ns UTC) to a Frankfurt session bar index: emits
bars_since_open:i64 = (local wall-clock minutes past the 09:00 open) /
period_minutes, in tz-aware DST-correct local time. So local 09:45 reads 3 in
both CEST (UTC+2) and CET (UTC+1) — the close-instant convention (spec 0050
§4.1). Trigger is an f64 Any input (value ignored, wired from close15) so the
node fires once per completed bar. Open/tz/period are baked structural config,
not scalar params (a timezone is not a scalar, C11). Admits chrono/chrono-tz to
aura-std — vetted DST math, never hand-rolled (per-case dep policy). Last node;
build-step 7 of milestone 'Strategy node vocabulary I'.
closes#90
Brummel
17197fed91