[CPritch]

Tiltpane plays something as the phone unlocks. Its first go moved the camera (a small zoom, or a lift), which didn't use the depth and felt flat next to the transitions. This adds effects that move through the scene itself.

• Effect (public): Ripple, Swell and Glint, with ALL and as_str() like Transition
• OutputRenderState::start_effect(effect, duration, origin): plays one over the wallpaper showing, starting from origin in screen uv. is_playing_effect() says whether one is going, and step_and_write reports a change while one plays, so it gets drawn
• Three new uniforms: effect, effect_progress and effect_origin. With no effect the shader takes the same path as before
• ripple: waves spread from the origin across the screen and back through the scene by depth rank at once, so they reach near things before far ones beside them, moving the picture to and from the origin and lighting their crests
• swell: a band rolls from the nearest things to the furthest by depth rank, each part of the scene leaning toward the viewer as it passes
• glint: a band of warm light passes back through the scene the same way, catching the brighter parts most
• Effects show over a wallpaper at rest, not during a transition, and each leaves it exactly as it was

shiftpaperd doesn't use any of this, so it looks the same.

Format, clippy and tests pass. New tests check the effect numbers match the shader, the names are unique, and the timing runs evenly to the end. Tiltpane builds against this branch, and on the emulator each effect plays on unlock as described. Not yet run on the Pixel or the desktop.