view: dimension names and units are guessed (a Torque shows in J) #2070

Found in the review of #2057, which adds the experimental view. It does not block that PR; #2059 fixed the findings that did. Paths refer to #2059's head.

Problem

The view model guesses a dimension name and a coherent unit for a value (CoherentUnits in crates/graphcal-project/src/view_model/value.rs). It disagrees with graphcal eval and with the declared type.

dim Torque = Force * Length;
node t: Torque = 2.0 N * 1.5 m;
node r: Dimensionless / Time = 2.0 / 1.0 s;

The numbers are right in the units shown. But showing a torque in joules goes against engineering practice, and the two commands disagree.

Proposed fix

Needs a decision on how the view shows units. The review recommends:

• dimension carries the declaration's own spelling (Torque, Dimensionless / Time).
• Without a display unit, a value is shown by the same rule as graphcal eval.