fix(website): cross-locale doc links + drop empty ko locale (#31895)

The locale switcher appeared broken because hardcoded markdown links
(`](/docs/X)`) got double-prefixed by Docusaurus to `/docs/<locale>/docs/X`
(404) in non-English locales, and the MDX hero `<a href>` on the index
page escaped locale routing entirely.

Changes:
- Rewrite 922 `](/docs/X)` -> `](/X)` across 166 docs files (strip trailing
  .md too). Docusaurus prepends locale + baseUrl itself.
- docs/index.md -> index.mdx; hero "Get Started" anchor -> Docusaurus
  <Link> so it stays inside the active locale.
- Drop `ko` locale entirely from docusaurus.config.ts + delete i18n/ko/
  (4 stale auto-translated kanban pages, <2% coverage, misleading).

Verified `npm run build` succeeds for both en and zh-Hans; `build/zh-Hans/
index.html` has no /docs/zh-Hans/docs/... double-prefixed paths.

PR2 will translate the 335 English docs into i18n/zh-Hans/.

website/docs/user-guide/features/memory-providers.md

@@ -537,7 +537,7 @@ echo 'SUPERMEMORY_API_KEY=***' >> ~/.hermes/.env
 
 ## Profile Isolation
 
-Each provider's data is isolated per [profile](/docs/user-guide/profiles):
+Each provider's data is isolated per [profile](/user-guide/profiles):
 
 - **Local storage providers** (Holographic, ByteRover) use `$HERMES_HOME/` paths which differ per profile
 - **Config file providers** (Honcho, Mem0, Hindsight, Supermemory) store config in `$HERMES_HOME/` so each profile has its own credentials
@@ -546,4 +546,4 @@ Each provider's data is isolated per [profile](/docs/user-guide/profiles):
 
 ## Building a Memory Provider
 
-See the [Developer Guide: Memory Provider Plugins](/docs/developer-guide/memory-provider-plugin) for how to create your own.
+See the [Developer Guide: Memory Provider Plugins](/developer-guide/memory-provider-plugin) for how to create your own.