Two follow-ups to the earlier /skewt work:
1. Interactive crosshair (matches the SPC-viewer feel from the
reference screenshot). Mousing over the diagram now drops a
horizontal pressure cursor with a top-left readout box showing the
pressure at the cursor's altitude (mb), the height in m and ft,
and the linearly interpolated temperature and dewpoint at that
level. Two coloured dots track the T and Td traces along the
cursor so the user can read the spread visually.
Mechanics: SkewtSvg.geometry/0 exposes the plot geometry (left,
right, top, bottom, p_bottom, p_top, t_min, t_max, skew) as JSON;
SkewtSvg emits an initially-hidden <g class="skewt-cursor"> layer.
A new Skewt hook in assets/js/app.ts inverts pressure_y to recover
pressure from the cursor's viewBox-Y, walks the (descending-pres-
sorted) profile to interp T/Td/height, and updates the elements.
The hook also handles mouseleave to hide the cursor and uses the
SVG's screen-CTM so the math stays correct under any container
aspect-ratio resize.
2. DB fallback for `available_valid_times`/`load_profile`. When the
on-disk `ProfilesFile` has nothing for the location-and-window
(true on dev, transient on prod between chain runs), SkewtLive
now falls back to `HrrrProfileLookup.{list_valid_times_near,
read_point_near}/3` against the `hrrr_profiles` Postgres table.
The lookup uses the same ±0.07° spatial tolerance and the
`(lat, lon, valid_time)` unique index that `Weather.find_nearest_
hrrr/3` already relies on, so the queries are index-only.
Returned shape matches `ProfilesFile.read_point/3` so SkewtLive
reads from either source transparently. NaiveDateTime → UTC
normalisation is centralised in `ensure_utc/1` so the LiveView
sees `%DateTime{time_zone: "Etc/UTC"}` regardless of which side
produced the value.
Tests: 6/6 new HrrrProfileLookupTest cases (list/limit/tolerance,
read nearest cell, nil for far cells, picks closest among matches),
3/3 SkewtLiveTest still green, 2,894 total Elixir tests + 221
properties green via mix test (one pre-existing flaky test in
admin/contact_edit_live re-runs clean). mix credo --strict clean.
mix assets.build clean.
Graham McIntire
a4cd7632eb