3D 3b1b-style ML clips + water-drop flow + seamless backgrounds

slides are now real Manim clips + interactive widget below

fix 14 medium review findings (correctness/robustness/a11y)

playground: browser-native narration (Web Speech) + optimized full-screen theater layout

playground: auto-fullscreen theater mode on Play all + slower comprehension pacing

Playground: whole-paper arc (problem→prior→method→results→graphs) + interconnected cards + detailed steps

Playground: one-click ▶ Play-all transport (web mirror of the video) + visual polish

deploy manimo concept playground (static)