text.setStyle now reads `size` and `tracking` with `number_given` and
`length_given` from pathops.rs instead of its own copies.
Both helpers read a string only when all of it is a number, or for
`length_given` a length with a unit (`"5 mm"`). Before, `"20abc"` read
as 20, so `text.setStyle` applied a 20 pt size and Offset Path a 10 pt
offset for `"10abc"`. Such a string is now refused with "`size` must be
a number, not \"20abc\"" and the document is left as it was.
object.path.offsetPath, object.path.simplify, object.path.splitIntoGrid,
object.path.cleanUp, object.pathfinder.trap and addon.contour.set read
their params with helpers that fell back to the default for a value of
the wrong type: "offset": true offset by 10 pt, "joins": 3 gave mitered
joins, "addGuides": "yes" added no guides. Each such value is now an
error naming the param, and the document and the undo history stay as
they were. An omitted or null param keeps its default, and a distance
still takes a string with a unit ("5 mm"). An unknown `joins` name is
refused as well.
Offset Path outlined an open path on both sides, so a shape whose last
anchor sits on its first came out as a ring with a hole. Such a path is
now offset as a closed shape: its last anchor merges into its first,
which takes the last anchor's in-handle, with the same 1e-6 test that
Object › Path › Join uses for one path (crates/engine/src/cmd/path.rs).
The Offset Path effect calls the same function.