Move ScalarFile from a dual-writer dual-format setup (ETF on the Elixir
side, materialized via NotifyListener; nothing on the Rust side) to a
single chunked-MessagePack format that both languages produce and
consume.
Elixir side:
- ScalarFile now writes gzipped MessagePack `.mp.gz` per chunk via
Msgpax. Reader decodes with Msgpax + zlib. Atom keys are stripped to
strings on encode and re-atomized via a whitelist on read so callers
see the same shape regardless of which side wrote the bytes.
- DateTime values round-trip through ISO8601 strings.
- New cross-language wire-format test that decodes a hand-rolled
payload mirroring exactly what `rmp_serde::to_vec_named` emits, so a
format regression on either side fails the suite.
Rust side:
- New `prop_grid_rs::weather_scalar_file` module:
- 1:1 port of `Microwaveprop.Weather.WeatherLayers.derive/1` plus
the surface fields `Weather.build_grid_cache_row/4` adds on top
(lapse rate, mid lapse rate, inversion strength + base, 850/700 mb
interpolation, surface RH, surface refractivity, ducting flag).
- `write_atomic` chunks rows into 5°×5° buckets, writes one
`<lat_band>_<lon_band>.mp.gz` per chunk via tmp + rename, drops
pre-existing chunks first to keep writes canonical.
- 5 unit tests covering surface-only rows, upper-air derivation,
write/read round-trip, chunk band boundaries, and the
out-of-physical-range surface-temp filter.
- Pipeline integration: both `run_chain_step` (f01..f18) and the f00
analysis path now build `Vec<ScalarRow>` in the same merged-cell
pass that builds `CellEntry` and `Conditions`, then fire a parallel
`spawn_blocking` write that overlaps with scoring. Awaiting the
scalar future after the score-band writes keeps the failure-surface
symmetric with the existing profile_future.
Result: every new forecast hour lands with the scalar artifact already
on disk, so /weather reads never fall through to ProfilesFile decode +
per-cell SoundingParams + WeatherLayers derivation. The Elixir-side
`NotifyListener.handle_propagation_ready/1` materialization remains as
an idempotent safety net for hours that pre-date this commit.
Graham McIntire
9f583a16bf