docs: remove mcp-bridge extension; harness reads compiler-generated config.json+prompt.txt

Agent-Logs-Url: https://github.com/github/gh-aw/sessions/c4564ad2-de2d-4e3d-8a0f-da65187abf59

Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>

Author: Copilot