Route assembly content synchronization through rad-app

[AJ-Koenig]

Summary

Make rad-app the assembly-content hub. This repository only notifies the hub after content changes; it never writes to another spoke. Synchronization uses reviewed staging PRs and preserves main release-promotion gates.

• Full mirror: assembly-docs/content contains every language and asset.
• Hardware spokes: assembly-docs contains only the matching product, with page.en.mdx mapped to page.mdx and meta.en.json mapped to meta.json.
• Product assets, KiCad files, and product-local BOM snapshots remain included.
• No initial content replacement or baseline seeding is performed by this PR.
• The notifier requires the existing RAD_VERSION_CONTROL_APP_ID variable and RAD_VERSION_CONTROL_PRIVATE_KEY secret, with the app installed for the hub and participating repositories.

Validation

• actionlint passed for the notifier.
• Hub verification passed: 23 synchronization tests, 3 BOM tests, OHAI type check, and full content validation.

Coordination

Hub implementation and rollout instructions: https://github.com/researchanddesire/rad-app/pull/1928

Merge through staging, promote the workflows to the default branch, then review the separately generated initial seed PRs before enabling routine content propagation.

Related implementation PRs

• https://github.com/researchanddesire/rad-app/pull/1928
• Route assembly content synchronization through rad-app #16
• https://github.com/researchanddesire/RADR-OSS/pull/8
• Route assembly content synchronization through rad-app OSSM#1
• https://github.com/researchanddesire/DT_Trainer-OSS/pull/20
• https://github.com/researchanddesire/Lockbox-OSS/pull/25