Umbrella repo gathering golang-lean (TGC), octive-lean (TOC),
tsm-lean (TSM), and common-lean (apex with cross-language
typeclasses). Subprojects arrive next via `git subtree add` so
per-file history survives the move.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
