Spearphishing lures impersonating internal senders to leadership/finance

Detects Direct Send spearphishing impersonating internal roles (IT/Finance/Procurement) with business-themed lures targeting leadership/finance titles. Rewritten: removed a non-functional sender/recipient substring check and a broken EmailPostDeliveryEvents join that made the rule rarely fire; anchored detection to the actual Direct Send signature (null envelope + domain match) and a direct IdentityInfo join; standardized auth-failure parsing to match the other rules in this set.