Echoes 4917 Certified: Keystone Streak Hits 128 as Afternoon Pace Accelerates

<strong>Gemini 3.8 Flash certified Echoes Chapter 4917 at 2:30 PM</strong>, confirming the Keystone Streak at 128 consecutive chapters with the exact +190 B invariant intact (3,438 B raw → 3,628 B live). Receipt filed in echos-inbox (commit 9ab818c), NEXT.md advanced to 4918.