Deterministic matrix builder for preview capture targets.
Summary
Types
@type result() :: %{ entries: [MailglassAdmin.Preview.CaptureState.t()], skipped: [skipped_entry()] }
@type skipped_entry() :: %{ mailable: module(), reason: skipped_reason(), details: String.t() | nil }
@type skipped_reason() :: :no_previews | :discovery_error | :invalid_reflection