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/developer-guide/model-provider-plugin.md

@@ -9,7 +9,7 @@ description: "How to build a model provider (inference backend) plugin for Herme
 Model provider plugins declare an inference backend — an OpenAI-compatible endpoint, an Anthropic Messages server, a Codex-style Responses API, or a Bedrock-native surface — that Hermes can route `AIAgent` calls through. Every built-in provider (OpenRouter, Anthropic, GMI, DeepSeek, Nvidia, …) ships as one of these plugins. Third parties can add their own by dropping a directory under `$HERMES_HOME/plugins/model-providers/` with zero changes to the repo.
 
 :::tip
-Model provider plugins are the third kind of **provider plugin**. The others are [Memory Provider Plugins](/docs/developer-guide/memory-provider-plugin) (cross-session knowledge) and [Context Engine Plugins](/docs/developer-guide/context-engine-plugin) (context compression strategies). All three follow the same "drop a directory, declare a profile, no repo edits" pattern.
+Model provider plugins are the third kind of **provider plugin**. The others are [Memory Provider Plugins](/developer-guide/memory-provider-plugin) (cross-session knowledge) and [Context Engine Plugins](/developer-guide/context-engine-plugin) (context compression strategies). All three follow the same "drop a directory, declare a profile, no repo edits" pattern.
 :::
 
 ## How discovery works
@@ -256,12 +256,12 @@ acme-inference = "acme_hermes_plugin:register"
 
 …where `acme_hermes_plugin:register` is a function that calls `register_provider(profile)`. The general PluginManager picks up entry-point plugins during `discover_and_load()`. For `kind: model-provider` pip plugins, you still need to declare the kind in your manifest (or rely on the source-text heuristic).
 
-See [Building a Hermes Plugin](/docs/guides/build-a-hermes-plugin#distribute-via-pip) for the full entry-points setup.
+See [Building a Hermes Plugin](/guides/build-a-hermes-plugin#distribute-via-pip) for the full entry-points setup.
 
 ## Related pages
 
-- [Provider Runtime](/docs/developer-guide/provider-runtime) — resolution precedence + where each layer reads the profile
-- [Adding Providers](/docs/developer-guide/adding-providers) — end-to-end checklist for new inference backends (covers both the fast plugin path and the full CLI/auth integration)
-- [Memory Provider Plugins](/docs/developer-guide/memory-provider-plugin)
-- [Context Engine Plugins](/docs/developer-guide/context-engine-plugin)
-- [Building a Hermes Plugin](/docs/guides/build-a-hermes-plugin) — general plugin authoring
+- [Provider Runtime](/developer-guide/provider-runtime) — resolution precedence + where each layer reads the profile
+- [Adding Providers](/developer-guide/adding-providers) — end-to-end checklist for new inference backends (covers both the fast plugin path and the full CLI/auth integration)
+- [Memory Provider Plugins](/developer-guide/memory-provider-plugin)
+- [Context Engine Plugins](/developer-guide/context-engine-plugin)
+- [Building a Hermes Plugin](/guides/build-a-hermes-plugin) — general plugin authoring