without
Return a copy of this with the snapshot for scenarioName removed, alongside the matching entry in RunResult.BatchCompleted.replicationsByItem. Returns null when the filter empties RunResult.BatchCompleted.snapshots — callers treat that as "the result is now empty; drop it".
Matching is by experiment.exp_name, which is the same key ScenarioOrchestrator uses when populating replicationsByItem. Returns the receiver unchanged when no snapshot carries scenarioName.
RunResult.BatchCompleted.summary is intentionally left untouched — it's an audit record of the batch that actually ran (item counts, begin/end times, etc.) and should not be rewritten to reflect a post-hoc deletion of one of its outputs.
Supports the Scenario app's identity-coupled lifecycle: when the user deletes a scenario from the editable list, the controller calls this to drop the corresponding completed snapshot from the in-memory result. Lives as an extension rather than a member so the data class itself doesn't grow per-host helpers; the helper is pure and has no Scenario-app coupling.