Domain-knowledge primer for the professional-services vertical (agencies, consulting firms, creative studios) so architect/pm don't spec naively against PSA incumbents (Scoro, Productive, Accelo, Ruddr, BigTime). Supplies the vocabulary, the non-obvious billing/margin rules, the entities a real proposal/portal/time/profitability product must model, and the per-product wedge. Applied by architect/pm during spec authoring for any of the four products in this vertical — proposals, client-portal, time-invoicing, profitability.