Select Headroom context engine on install

fix(openclaw): proxyPort only applies to local URLs, consistency pass

feat(openclaw): support remote Headroom proxy (connect-only)

docs: add OpenClaw plugin section to main README

Restore pythonPath and proxyPort config support

Auto-detect proxyUrl by default and keep explicit override

Add controlled proxy autostart and unsafe-install guidance

Harden openclaw plugin proxy handling and metadata

feat: add OpenClaw ContextEngine plugin (@headroom-ai/openclaw)