- identify_var: full round-trip across every known (discipline,
category, number) triple, plus a property that any triple outside
the 12-entry lookup falls back to the "cat:num" default.
- identify_level: hybrid-level and entire-atmosphere branches, plus
two properties — pressure levels always render as
`div(value_pa, 100) <> " mb"` and unknown surface types always
render as `unknown:<type>:<value>` (generator samples only from
types outside the 6-entry lookup set).
- sign_magnitude_16: round-trip property over [-32_767, 32_767] (±0
both decode to 0 as intended) and a monotonicity property inside
a single sign band.
Suite: 2,419 tests + 164 properties (was 2,416 + 159); credo strict
clean.