fix(render): A7 Fix D D-1 — clamp the point-light sum on its own (#140)

accumulateLights folded ambient+sun+torches into one accumulator clamped only
in the frag, so a few warm intensity-100 torches blew walls/objects to white.
Mirror retail SetStaticLightingVertexColors: sum point/spot into pointAcc, clamp
to [0,1] (the baked emissive), THEN add ambient+sun, frag final-clamps. Matches
LightBake.ComputeVertexColor (LightBakeConformanceTests). Per-light cap unchanged.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/AcDream.App/Rendering/Shaders/mesh_modern.vert

@@ -183,29 +183,33 @@ vec3 pointContribution(vec3 N, vec3 worldPos, GlobalLight L) {
 vec3 accumulateLights(vec3 N, vec3 worldPos, int instanceIndex) {
     vec3 lit = uCellAmbient.xyz;
 
-    // SUN / directional — from the SceneLighting UBO (global; the audit cleared
-    // the ambient + sun chain as already faithful). Any point/spot entries still
-    // present in the UBO from LightManager.Tick are IGNORED here — point lights
-    // now come per-object from the SSBO below, so there's no double-count.
+    // SUN / directional — material-lit term (added with ambient, NOT into the
+    // torch sum), unchanged.
     int activeLights = int(uCellAmbient.w);
     for (int i = 0; i < 8; ++i) {
         if (i >= activeLights) break;
         if (int(uLights[i].posAndKind.w) != 0) continue;   // directional only
-        vec3 Ldir = -uLights[i].dirAndRange.xyz;           // forward points INTO the scene
+        vec3 Ldir = -uLights[i].dirAndRange.xyz;
         float ndl = max(0.0, dot(N, Ldir));
         lit += uLights[i].colorAndIntensity.xyz * uLights[i].colorAndIntensity.w * ndl;
     }
 
-    // POINT / SPOT — THIS object's selected set (minimize_object_lighting): 8 int
-    // slots per instance into the global light buffer, -1 = unused. Camera-
-    // independent, so a wall's torches light it the same regardless of viewer pos.
+    // POINT / SPOT torches: their OWN accumulator (A7 Fix D, D-1). Retail's
+    // SetStaticLightingVertexColors sums the static point lights from BLACK and
+    // clamps the SUM to [0,1] before anything else (a baked emissive term), so a
+    // few warm intensity-100 torches can't push the whole pixel to white the way
+    // folding them into ambient+sun did. Mirrors LightBake.ComputeVertexColor
+    // (LightBakeConformanceTests). Per-light cap inside pointContribution is unchanged.
+    vec3 pointAcc = vec3(0.0);
     int base = instanceIndex * 8;
     for (int k = 0; k < 8; ++k) {
         int gi = instanceLightIdx[base + k];
         if (gi < 0) continue;
-        lit += pointContribution(N, worldPos, gLights[gi]);
+        pointAcc += pointContribution(N, worldPos, gLights[gi]);
     }
-    return lit;
+    lit += min(pointAcc, vec3(1.0));   // clamp the torch sum on its own (retail baked emissive)
+
+    return lit;                        // frag still does the final min(lit, 1.0)
 }
 
 out vec3 vNormal;