## Summary
- Add `README.ko.md` as a Korean translation of the root README.
- Add a centered language switcher block to `README.md` and
`README.ko.md`.
- Keep the change small and docs-only (no code/runtime behavior
changes).
## Motivation
I am a Korean developer and a frequent Wave Terminal user.
I read the README often, and noticed there was no Korean README
available, so I prepared this translation to improve accessibility for
Korean users.
## Ongoing Contribution Intent
As an active Wave Terminal user, I can continue contributing incremental
Korean localization updates after this PR is reviewed.
## Scope Notes
- One logical change in a single PR.
- Focused only on documentation, aligned with the contribution guide for
small, obvious docs improvements.
