Three additions that bring the diagram closer to the SPC sounding
viewer's full-information chart:
* Wet-bulb temperature trace, plotted as a thinner blue line under
the dewpoint trace. Comes from a Stipanuk-style bracket between
the level's dewpoint and dry-bulb temperatures (already used by
`SkewtParams` for the wet-bulb-zero level — now public so the
renderer can call it per level).
* Environment virtual-temperature trace and parcel virtual-T
trajectory, both as thin pinkish dashed lines. The parcel
virtual-T is the actual buoyancy curve CAPE integrates against,
so showing it next to the dry-bulb parcel ascent makes the
moisture correction visible. New `SkewtParams.virtual_temp_c/2`
and `/3` helpers, plus `SkewtParams.mixing_ratio/2`.
* Critical-level rail on the right edge. Each of LCL / LFC / EL /
0 °C / WBZ that resolves on the current profile gets a short
horizontal tick at the right of the plot and a `<label> <p> mb`
tag just outside it — matches the SPC chart's `143 mb (mix)` /
`158 mb (mix)` annotation column. SkewtLive computes the
pressures (and converts the height-keyed 0 °C and WBZ from
SkewtParams back to pressure via `pressure_at_height/2`) before
handing them to `SkewtSvg.render/2`.
Wind-derived overlays (hodograph, wind barbs) remain off — HRRR
profile data is wind-free above 10 m AGL.
mix test: 27 / 27 across the four /skewt-related test files,
2,902 / 2,902 + 221 properties on the full suite. mix credo --strict
clean (one cyclomatic-complexity refactor extracted along the way).
Graham McIntire
77bc894f56