G1: preserve GPU Posterize threshold parity

Use an explicit FMA for the final quotient correction at Posterize
boundaries. Align the kinetic motion-blur QA comparison with export
settings and credit sanyamsingh001.

Co-authored-by: Codex <[email protected]>

contributors/people.toml

@@ -29,3 +29,7 @@ sync_github_name = false
 
 [people.jonassneu]
 sync_github_name = true
+
+[people.sanyamsingh001]
+display_name = "sanyamsingh001"
+sync_github_name = false

crates/automation/tests/qa/kinetic.rs

@@ -71,6 +71,8 @@ fn kinetic_typography() {
     // A precomp of everything, time-remapped to play backwards.
     let pre = qa.exec("layer.precompose", json!({"layers": ["Title", "Sub"], "name": "Type Pre", "mode": "move"}));
     assert!(pre["comp"].is_u64() && pre["layer"].is_u64(), "{pre}");
+    // Nested switches pass the precomp layer's blur flag down to the animated title.
+    qa.exec("layer.setSwitch", json!({"layers": [pre["layer"].clone()], "switch": "motionBlur", "value": true}));
     qa.exec("layer.enableTimeRemap", json!({"layers": [pre["layer"].clone()], "value": true}));
     qa.tool("add_keyframe", json!({"layer": pre["layer"].clone(), "path": "timeRemap", "keys": [{"time": 0, "value": 1.9}, {"time": 1.9, "value": 0}]}));
     let fwd = qa.frame(Some(pre["comp"].clone()), 1.6);

crates/gpu/src/shaders/fx_stylize.wgsl

@@ -40,7 +40,7 @@ fn fxs_smoothstep(e0: f32, e1: f32, x: f32) -> f32 {
 fn fxs_qdiv(x: vec3<f32>, a: f32) -> vec3<f32> {
     let q = x / a;
     let r = fma(-q, vec3<f32>(a), x);
-    return q + r / a;
+    return fma(r / a, vec3<f32>(1.0), q);
 }
 
 fn fxs_rem2(i: i32) -> i32 {