#2252 docs: add Korean README and core guides

Description

## Summary

Add a Korean entry point for Strata and translate the four user-facing guides needed to install, choose, understand, and troubleshoot it.

## What changed

- add `README.ko.md`
- add Korean versions of `INSTALL.md`, `MODELS.md`, `TROUBLESHOOTING.md`, and `HOW_IT_WORKS.md`
- add Korean language links to the existing README translations and the four English guides
- route the Korean README to the Korean guides where available

## What this leaves alone

- no code, setup behavior, defaults, model choices, or benchmark numbers change
- detailed and hardware-specific guides remain in English

## Checks

- matched headings, tables, and code-block structure against each English source
- checked 110 local file and Korean heading-anchor links
- rendered all five Korean files with the local GFM-compatible `marked` parser
- `git diff --check`