chore: sync develop into main (docs + release governance updates) (#53) (#54)

* ci: add separate main-to-develop backmerge workflow for non-hotfix merges

* ci: handle fork develop branch names in backmerge sync guard

* docs: refresh release docs metadata, module paths, and Claude integration link

* docs(deploy): restore CLAUDE_CODE_WHITELIST.md at canonical path

* docs(reference): add API_REFERENCE.md compatibility shim

* docs(reference): mirror full api-reference content to API_REFERENCE.md

* governance: establish two-repo public promotion contract and automation

* governance: transition to single-repo public release model

* docs(reference): convert API_REFERENCE.md to compatibility stub

* docs(reference): remove API_REFERENCE.md and normalize canonical API links

Author: T72