Move the 27 internal design docs (87 tracked files) from docs/ to dev-docs/
to make room for the public documentation site, adjust Docker/fnOS ignores,
refresh the README/AGENTS/ARCHITECTURE references, and land the docs
workflows ahead of the subtree import so they cannot diverge from mirror.
Co-Authored-By: Mika (Multica) <[email protected]>
Co-authored-by: multica-agent <[email protected]>
