Check if spectators receive `UnitDamaged`

Here's a claim that they don't: https://github.com/beyond-all-reason/Beyond-All-Reason/issues/6419

Start by reading the claim in Beyond All Reason issue #6419 and locating the UnitDamaged event handling and spectator delivery path in RecoilEngine. Verify whether spectators receive the event, then document the result or identify the needed behavior change; the issue is complete when this behavior is confirmed and any required fix is covered by an appropriate test.

Written by the indexing model from the issue text.