Misc · Numbers: a result goes on whole; long readings wrap

A calculator result stays in the sum as `a`, handed to evaluate with
its whole value, so 1 ÷ 3 = × 3 = gives 1; sign turns it and delete
takes it. Equals waits on a dangling operator. The converter's reading
wraps in its box rather than ending in an ellipsis, and tests hold
Control, the = key, a point after a result and the six digits.

tasks/ch31-43.md

@@ -315,8 +315,8 @@
 
 ## T42b Misc · Numbers
 
-- [x] Calculator → `misc::Calculator`: digits, the four operations in precedence through `forms::evaluate`, sign, delete and clear, twelve significant digits; keys type too, and Enter gives the result while the calculator itself has focus
-- [x] UnitConverter → `misc::UnitConverter`: length, area, volume, mass, temperature, speed and data, each on a starting pair, with a swap; six significant digits
+- [x] Calculator → `misc::Calculator`: digits, the four operations in precedence through `forms::evaluate`, sign, delete and clear; a result goes on at its whole value and shows twelve significant digits; keys type too, and Enter gives the result while the calculator itself has focus
+- [x] UnitConverter → `misc::UnitConverter`: length, area, volume, mass, temperature, speed and data, each on a starting pair, with a swap; six significant digits, wrapped when long
 
 ## T42c Misc · Codes and checks