Add shoreline facility

shaders/ppi_shoreline.frag

@@ -0,0 +1,20 @@
+#version 330 core
+// Feature 9: PPI Shoreline / Terrain — fragment stage
+// Active points render in P7 blue; fading points render in P7 greenish-yellow
+// with brightness proportional to vFade.
+in float vFade;
+in float vActive;
+
+uniform vec3 uActiveColor;   // P7A blue
+uniform vec3 uPersistColor;  // P7P greenish yellow
+
+out vec4 fragColor;
+
+void main()
+{
+    if (vFade <= 0.01) discard;
+    vec3 col = (vActive > 0.5)
+        ? uActiveColor
+        : uPersistColor * vFade;
+    fragColor = vec4(col, vFade);
+}