Surfaced by the measurement-milestone fieldtest: a downstream author
reaching for session anchoring or declared taps had no public statement of
either — the semantics lived only in node source / the design ledger.
SessionFrankfurt / Session output semantics:
- glossary `session node`: corrected — it claimed three streams
(`bars_since_open`, `in_session`, `session_open_ts`), but the shipped node
emits ONE `i64` field `bars_since_open`. Now states the real contract: the
count of completed bar-periods since the local (tz-aware, DST-correct)
session open, close-instant indexed (09:15->1, 09:45->3; pre-open <=0), with
the Frankfurt 09:00 Europe/Berlin open + `period_minutes` knob + the
value-ignored `trigger`.
- authoring-guide: a "Session anchoring: the SessionFrankfurt preset"
subsection — schema (trigger / period_minutes / bars_since_open), the
close-instant multiples, the EqConst gating pattern, DST handling, and the
add-snippet. Verified against `aura graph introspect --node SessionFrankfurt`.
Declared-tap authoring (C27 / the #284 tap op):
- authoring-guide: the `tap` op-table row (seven ops -> eight) + a worked
"declaring a measurement tap" example. The example is verified: piping it
through `aura graph build` emits
`taps:[{"name":"spread","from":{"node":2,"field":0}}]`.
- design ledger op-list (INDEX.md): a `tap` bullet (seven verbs -> eight);
also corrected the `expose` "only verb that keeps `as`" claim — `tap` keeps
it too.
- README op-kind enumeration: adds `tap`.
Docs only; no code change. Both worked examples were run through the built
`aura` binary; the SessionFrankfurt schema was checked against introspect.
closes#285
claude
a5e02ff541