A center-anchored module is mounted twice: the copy that is drawn, and a
zero-size placeholder holding its place in the flow beside the anchor.
findPanelWidget returned whichever registered first, and that order is
not stable across a live bar reconfiguration, so a panel could open
anchored to the invisible copy -- mispositioned, with the drawn slot
never lighting up and switchPanelFrom unable to find it again.
The mark was also always 55% of the slot, which fits an icon but
underlines only a fraction of a text label, and runs the full height of a
multi-line module on a vertical bar. Modules can now say how long the
mark should be along the bar; anything that does not answer keeps the old
proportion.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
