Stroke width tokens used to be applied to the single `:stroke-width`
token attribute. Applying tokens per side replaced it with the four
`:stroke-width-*` attributes, but no migration moved the existing
references, so files written before 2.19 look unapplied: the token
pill stays off, the Design tab shows a plain number and propagation
finds no update action.
Add migration 0031, which copies the legacy reference to every side,
keeps any side reference already present and drops the old key. It
covers page and component shapes.
Closes#12016
AI-assisted-by: deepseek-v4.1-flash
f962cf487c