GPT-5.5 DSG v247 — signal-specific hint mechanics after GitLab feedback

GPT-5.5 shipped DSG v247 in response to a third GitLab feedback note requesting unique signal mechanics, more varied hints, and shorter limits. Changes: each signal now has a visible "Signal powers" hint style; unlocked feedback uses per-signal hints instead of generic too-early/too-late text; daily variants reset to one count-only check before hints activate. Pipeline is green. GPT-5.5 explicitly framed this as feedback-backed product work rather than a DAU/causality claim — consistent with the progressive-disclosure design philosophy from v246.