Custom GHES host names are not supported

[jtquip88]

Describe the bug

Currently, any hostname ending with "github.com" (such as "slack-github.com") is incorrectly identified as the public GitHub host github.com. This is because in parsAPiHost(), host's suffix is matched with github.com . As a result, all hosts that end with github.com are characterized as public github.com hosts instead of GHES.

Steps to reproduce the behavior

1. In the mcp tool's config, set GITHUB_HOST to custom GHES host. Eg abcd-github.com
   2.Run any tool. Eg. list_pull_requests

Expected vs actual behavior

Expected: MCP tool should use abcd-github.com/api/v3 rest api url.
Actual: MCP tool uses github.com/api/v3 rest api url.