[JSDoc] Improve JSDoc comments for coding agents

EUI JSDoc coverage is incomplete. Coding agents working in Kibana, Cloud UI and other consumers can inspect the installed `@elastic/eui` version directly and derive the knowledge from JSDoc.

## Goal

Improve JSDoc so agents can understand and use EUI APIs without searching external documentation:

- add a concise summary for each public component, utility and service
- document all public props and parameters accurately
- add `@example` blocks showing common usage
- redirect to component's specific documentation page
- redirect LLMs to MDX file in EUI monorepo
- resolve relevant TypeDoc warnings (these may help identify missing or invalid JSDoc, not every warning indicated missing docs)

## Context

### typedoc

The purpose of this task is to resolve `typedoc` warnings. Some of them might be relevant for us while some [can be silenced](https://typedoc.org/documents/Options.Validation.html).

You can see the warnings by running `yarn workspace @elastic/eui-docgen build` from the root folder.

## Acceptance criteria

- [ ] Public APIs in the agreed scope have useful summaries
- [ ] Public props and parameters are documented accurately
- [ ] Common usage is represented with `@example` blocks
- [ ] Relevant TypeDoc warnings are resolved
- [ ] Remaining warnings are reviewed and intentionally suppressed or tracked