fix(ui5-illustrated-message): vertical responsiveness corrected

[kineticjs]

Fixes: 12673

Problem:
When design is Auto, ui5-illustrated-message automatically selects the illustration size (Scene/Dialog/Spot/Dot/Base) by comparing the container width and height with fixed breakpoints. The fixed height thresholds, however, cannot alone reliably determine the correct size because, besides the illustration, the component can also contain a title, subtitle, and actions of arbitrary height.

Solution:
Replace checks against fixed height thresholds with a check of whether the actual content height (illustration + title + subtitle + actions) fits within the container at the current illustration size — decreasing the size if the content overflows.
This also makes the workaround for issue #5852 (where content flickered endlessly between showing and hiding a vertical scrollbar) redundant, since vertical responsiveness now ensures no scrollbar appears in the first place.

[sap-ui5-webcomponents-release]

🚀 Deployed on https://pr-13795--ui5-webcomponents-preview.netlify.app

[NakataCode]

Two things that are worth checking:

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1. Height cache after theme change

Theme changes re-render via renderDeferred without going through _invalidate, so onInvalidation never fires and _contentHeightForMedia isn't cleared. If a larger-font theme caused a downgrade (e.g. "scene" → "dialog"), switching to a smaller-font theme keeps the stale cached height, and _applyMedia will keep rejecting "scene" even though it would now fit. Since _checkHeightConstraints only writes to the cache on overflow, and the downgraded media fits, nothing re-measures until a resize or content change.

2. Height adaptation for fixed (non-Auto) designs

The old code called _adjustHeightToFitContainer() for all fixed designs, which added the fit-content class so the SVG could scale down into small containers. Now the height logic only runs for design === Auto, and the fit-content CSS was removed. So a fixed design="Dialog" in a small container (e.g. 200px) would overflow instead of scaling the illustration.