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/guides/delegation-patterns.md

@@ -8,7 +8,7 @@ description: "When and how to use subagent delegation — patterns for parallel
 
 Hermes can spawn isolated child agents to work on tasks in parallel. Each subagent gets its own conversation, terminal session, and toolset. Only the final summary comes back — intermediate tool calls never enter your context window.
 
-For the full feature reference, see [Subagent Delegation](/docs/user-guide/features/delegation).
+For the full feature reference, see [Subagent Delegation](/user-guide/features/delegation).
 
 ---
 
@@ -254,4 +254,4 @@ delegation:
 
 ---
 
-*For the complete delegation reference — all parameters, ACP integration, and advanced configuration — see [Subagent Delegation](/docs/user-guide/features/delegation).*
+*For the complete delegation reference — all parameters, ACP integration, and advanced configuration — see [Subagent Delegation](/user-guide/features/delegation).*