fix(web-components): #4451 preserve dialog content semantics

[sylvesterkaczmarek]

Summary of the changes

Remove the forced aria-describedby from IcDialog's native dialog element so structured slotted content is not flattened into a single screen-reader description.

This keeps aria-labelledby for the dialog heading/label and allows links and other semantic content to remain navigable.

Added:

• unit regression coverage with structured dialog content and a link
• React/Cypress accessibility coverage confirming aria-describedby is omitted, heading labelling is preserved, the slotted link remains focusable, and axe passes

This follows WAI-ARIA APG guidance to omit aria-describedby when dialog content contains semantic structures that need to be navigated.

Related issue

Closes #4451

[sylvesterkaczmarek]

Thanks. I’ve rebased this onto current develop, split the change into web-components and react commits, regenerated the 12 snapshots affected by removing the dialog aria-describedby, and fixed the Cypress assertion chaining issue. The full web-component suite passes with the updated snapshots, the focused structured-content Cypress regression passes, and Prettier, Commitlint, the scope checker, and both package builds pass. CLA is green.