Preserve execution provenance when simplifying preview-heavy workflows

When a preview screen also acts as the commit boundary for an immutable execution manifest, removing the preview UI must not remove that boundary. Move manifest creation into the remaining explicit selection action, retain manifest identity and digest through launch, and invalidate both selection and manifest whenever any input filter changes or a refresh fails. This applies to reproducible batch workflows where execution must be tied to frozen inputs; purely cosmetic previews do not need persistence.

Evidence/example (2026-09-11; repository implementation and local/CI verification): During a dashboard simplification, the preview table, pagination, history surface, and advanced sampling controls were removed. The replacement “Get calls” action remained bounded to the launch limit, created an immutable cohort manifest, selected the returned call IDs, and cleared launchability on stale filters or errors. Independent review plus 288 relevant tests and the repository CI verify job passed before merge.