docs: fix mkdocs build errors

- Add EMAIL_SEARCH_PERFORMANCE.md to nav configuration
- Fix broken reference to ../README.md by using GitHub repo link instead

This resolves the mkdocs build failure in strict mode where undocumented files
and relative links outside the docs directory are not allowed.

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

Author: 2 people

docs/EMAIL_SEARCH_PERFORMANCE.md

@@ -203,4 +203,4 @@ A: Technically yes, but it's not recommended for mailboxes > 50,000 emails. Use:
 ## See Also
 
 - [IMAP RFC 3501](https://tools.ietf.org/html/rfc3501) - IMAP Protocol Specification
-- [mcp-email-server Configuration Guide](../README.md)
+- [mcp-email-server Repository](https://github.com/ai-zerolab/mcp-email-server) - Main project

mkdocs.yml

@@ -9,6 +9,7 @@ copyright: Maintained by <a href="https://ai-zerolab.com">ai-zerolab</a>.
 
 nav:
   - Home: index.md
+  - Email Search Performance: EMAIL_SEARCH_PERFORMANCE.md
   - Modules: modules.md
 plugins:
   - search