docs: fix stale client repo entry in llms.txt, point agents at shipped SDK guidance

[WiktorStarczewski]

Two changes to static/llms.txt.

The miden-client entry is wrong

- [miden-client](https://github.com/0xMiden/miden-client): Rust client, Web SDK, and React SDK.

That repository was renamed — https://github.com/0xMiden/miden-client 301s to 0xMiden/rust-sdk — and it no longer contains the Web SDK or the React SDK, which live in 0xMiden/web-sdk. So the one line an agent would follow to find the TypeScript SDK source sends it to a repo that does not have it, and the redirect hides the problem rather than surfacing it. Split into two accurate entries.

The other seven repository links check out fine (all 200, no redirects).

Agents should know the SDK ships its own guidance

As of web-sdk#310, each @miden-sdk/* package publishes an AGENTS.md index and a skills/ directory inside its npm tarball. The point is version-matching: an agent working in a consumer's repo gets guidance for the release in that repo's lockfile, rather than whatever its training data remembers or whatever this site currently documents. For API specifics that is strictly better than a docs page, which can only describe one version.

Added a line under the header pointing there, framed so an agent reading llms.txt knows to prefer it for JavaScript and React work.

Notes

• llms-full.txt is still absent (404). Worth adding, but it wants generation from the Docusaurus build rather than a hand-maintained static file, so it is out of scope here.

Test plan

• https://github.com/0xMiden/rust-sdk and /web-sdk both return 200 with no redirect
• https://docs.miden.xyz/llms.txt serves the updated file after deploy