The cycle-0047 typed-Scalar params migration (86746e3) changed each
RunManifest param value on the C18 flat runs store from a bare JSON
number (2.0) to an externally-tagged Scalar ({"F64":2.0}), but did not
migrate the persisted runs.jsonl. Registry::load could no longer
deserialize any pre-0047 line, so `aura runs list` / `runs rank` errored
out on a researcher's existing run history (bug F5, surfaced by the
"The World, part II" milestone fieldtest).
Fix: a localized read-side back-compat mirror (src/compat.rs). load()
now reads each line via RunReportRead, whose ScalarRead accepts BOTH the
tagged form AND a bare JSON number (coerced to Scalar::f64), then
converts into the canonical RunReport. The forward write path (append /
RunReport::to_json) is untouched — it still emits the tagged form. This
is a one-directional read widening, not a format change.
The secondary clause of #83 (parse error exits 0) was triaged as
not-a-bug: runs list/rank already exit 2 via load_runs_or_exit
(main.rs:742); the "(exit 0)" in the fieldtest transcript was a pipe
measurement artifact ($? read head's exit code, not the binary's).
RED test (committed 20511d5) now green; full workspace suite + clippy
green.
closes#83
Brummel
58bff32e6a