Art(shader): Emissive-Gloam master shader (in-shader flicker cadence)

ProjectM/EmissiveGloam — URP HLSL, HDR emission (Bloom-catching), with the
readability 'steady=true / flicker=false' channel as a material param
(_FlickerAmount), no script. Applied to the staging flora bulbs (cold, flicker).
The other two master shaders already exist (Lit URP graph, AnimatedLitShader).

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

Assets/_Project/Art/Materials/Staging/M_EmissiveGloam_Flora.mat

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+    m_Floats:
+    - _FlickerAmount: 0.35
+    - _FlickerSpeed: 5
+    - _Seed: 0
+    m_Colors:
+    - _EmissionColor: {r: 0.28, g: 2.1000001, b: 3.5, a: 3.5}
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Assets/_Project/Shaders/EmissiveGloam.shader

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+// Emissive-Gloam — the LANTERN "true vs false light" master shader.
+// One shader is the whole palette rule: hue = warm(ours)/cold(gloam)/lure; and the
+// load-bearing readability channel is CADENCE — _FlickerAmount 0 = STEADY (true light),
+// >0 = guttering FALSE light. Flicker lives in-shader (uses _Time), so it needs no script
+// and reads in edit + play. HDR emission so URP Bloom catches it. Unlit: these are glows.
+Shader "ProjectM/EmissiveGloam"
+{
+    Properties
+    {
+        [HDR] _EmissionColor ("Emission (HDR)", Color) = (0.1, 0.8, 0.5, 1)
+        _FlickerAmount ("Flicker Amount (0=steady/true, 1=false)", Range(0,1)) = 0.0
+        _FlickerSpeed ("Flicker Speed", Float) = 6.0
+        _Seed ("Per-material phase seed", Float) = 0.0
+    }
+    SubShader
+    {
+        Tags { "RenderType"="Opaque" "RenderPipeline"="UniversalPipeline" "Queue"="Geometry" }
+        Pass
+        {
+            Name "EmissiveGloamUnlit"
+            Tags { "LightMode"="UniversalForward" }
+            HLSLPROGRAM
+            #pragma vertex vert
+            #pragma fragment frag
+            #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Core.hlsl"
+
+            struct Attributes { float4 positionOS : POSITION; };
+            struct Varyings   { float4 positionHCS : SV_POSITION; };
+
+            CBUFFER_START(UnityPerMaterial)
+                half4 _EmissionColor;
+                half  _FlickerAmount;
+                half  _FlickerSpeed;
+                half  _Seed;
+            CBUFFER_END
+
+            Varyings vert (Attributes IN)
+            {
+                Varyings OUT;
+                OUT.positionHCS = TransformObjectToHClip(IN.positionOS.xyz);
+                return OUT;
+            }
+
+            half4 frag (Varyings IN) : SV_Target
+            {
+                float t = _Time.y * _FlickerSpeed + _Seed;
+                // layered sines -> an organic guttering wave in [-1,1]
+                float wave = 0.6 * sin(t) + 0.4 * sin(t * 2.37 + 1.3);
+                // f = 1 when steady (_FlickerAmount==0); dips toward (1-_FlickerAmount) as it gutters
+                float f = 1.0 - _FlickerAmount * (0.5 - 0.5 * wave);
+                return half4(_EmissionColor.rgb * f, 1.0);
+            }
+            ENDHLSL
+        }
+    }
+    Fallback Off
+}

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