ci: publish weekly M0 research source snapshot

[Pigbibi]

Summary

• build a closed M0 research source snapshot immediately after the existing weekly advisory report
• include it in the existing weekly artifact with no schedule, input, or site-publication change

Safety

• source generation is offline and no-order only
• no cross-repository delivery, secret, runtime, platform, broker, or execution path is added

Validation

• diff check passed locally
• GitHub CI will validate workflow syntax and repository tests