[borismasis]

Opening or changing a slider comparison could briefly show the original alone with the curtain hidden, the previous comparison at the next framing, a black frame, or a first frame with the default curtain while the next pair loaded.

Changes

• SliderComponent.preload(ids) caches a pair, including image assets, without showing it, so a following configure with the same ids switches within one frame.
• Pair options (viewAligned, mode, viewScale, viewCorrection, visibility) apply only once the state shows the configured pair; the shown pair keeps its own options while the next one loads.
• A cached pair swaps before the next frame (new StateService.lastState$, the replayed latest frame).
• The slider leaves traversal before changing the trajectory, and a newly activated slider applies its curtain together with its first GL update.
• SliderGLRenderer.render clears before drawing, so it never composites over another background renderer still active in the same frame.
• A disposed TextureProvider ignores late region-of-interest updates and tiles instead of throwing on its released renderer.

Testing

• yarn lint, yarn build, yarn test (1,735 tests, 128 suites) pass locally.
• New tests: SliderPreload, SliderPairConfiguration, SliderExclusiveBackground, TextureProviderDisposed; updated SliderSelectionFraming, SliderAutomaticMotion, SliderViewAligned.
• Checked in a Time Travel app with per-frame canvas captures: one visual change per comparison switch and a single-step entry.