OperationAttention

A one-shot ATTENTION request (#264 inbound) — fired MID-flight to pull the user BACK to a tracked operation that needs them (a protocol step waiting on their input, a counterparty's move). Distinct from OperationOutcome, which fires when the op FINISHES. The presentation edge turns it into a heads-up notification and decides whether to suppress it (e.g. when the app is already foreground — no point summoning someone who's looking). title/body are caller-provided; contentIntent taps back to the op's screen.