- connect_account.feature: refine the burst scenario to "best recent" (likely-good selection, skips too-short/too-long) and add a scenario for the stronger model. - scenario_coverage: remap to TestOnboardBurstVideoIDs + add the model scenario (the old NewestUnsummarizedVideoIDs test was removed). - architecture.md: new "Connect-time onboarding burst" subsection — junk-avoiding selection over persisted duration, the burst-only stronger-model chain, and why has-captions/cached-first are not selection signals.