Finds why Google Ads serving or reporting changed, working the clue levels in dependency order, account status then campaign status reasons then disapprovals then budget then rank then destination then learning state, keeping what is observed separate from what is merely suspected. Use when impressions, clicks, spend or conversions fall without an obvious reason. Boundary: `conversion-funnel` hunts drop-off in an owned funnel and `product-catalog-audit` tracks shopping disapprovals over time; this diagnoses one account's serving now.
