Add MCP ToolHive examples

[hsteude]

Summary

• Add top-level MCP server examples under mcp-servers/.
• Add deploy-upstream-mcp-server with a minimal upstream Time MCPServer manifest.
• Add build-custom-mcp-server with a compact FastMCP workspace-runbooks server, Dockerfile, PVC-backed ToolHive manifest, and seed Markdown runbooks.
• Keep commands notebook-friendly by relying on the current workspace kubectl context instead of requiring a NAMESPACE variable.
• Update the examples README with the new MCP server example category.

Verification

• PYTHONPYCACHEPREFIX=/var/folders/b7/dn6zlyjs74g3m2569m6wx_vr0000gn/T/opencode/pycache python -m py_compile mcp-servers/build-custom-mcp-server/runbook-server/server.py
• git diff --check

Not run

• docker build -t mcp-servers/build-custom-mcp-server/runbook-server: Docker daemon is not running locally.