A texture object handed to a widget's texture setter stayed on its old frame and layer: Button and CheckButton slots only stored it, and StatusBar, Slider and ColorSelect ignored a texture object altogether.
In the reference, each setter deletes the slot's old texture and re-links the new one into the widget: Button states on ARTWORK, the highlight on HIGHLIGHT with its blend, checked textures, thumbs and markers on OVERLAY, the bar on the given layer. The link writes the texture's shown bit, and the old parent's removal hook runs. Thumbs and markers lose their anchors.
All these setters now go through one install that re-links through the region owner path and writes the shown bit; a non-current state texture answers `IsShown()` nil until its state comes, and the raise texts are the client's.
Tests cover each setter, both shown-bit directions and the backdrop teardown.
Fixes#902
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
