Add MCPX server config example

[itsablabla]

Summary

• Add a project-scoped Codex MCP config for the mcpx server.
• Add a generic MCP client JSON example for the same server.
• Keep the Lunar API key out of Git by sourcing x-lunar-api-key from MCPX_LUNAR_API_KEY.

Verification

• jq . configs/mcp/mcpx.mcp.example.json
• jq -e '.mcpServers.mcpx.url == "https://garza-mcp.exe.xyz/mcp" and .mcpServers.mcpx.headers["x-lunar-api-key"] == "${MCPX_LUNAR_API_KEY}"' configs/mcp/mcpx.mcp.example.json
• codex mcp list shows mcpx enabled from the project config.
• codex mcp get mcpx shows env_http_headers: x-lunar-api-key=MCPX_LUNAR_API_KEY.
• rg secret scan for the provided key value returned no matches.

Browser Verification

• /browser, /screenshots, /demo, and /browser-profiler were not applicable because this is a static config-only change with no UI route or browser interaction surface.

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[charliecreates]

Reviewed the latest changes, and I don’t have actionable feedback to address.