Move the components into their own module

This makes the module tree more reflective of module use patterns. In
particular, it restores the condition that every top-level module is
used in top-level code, which was broken by the addition of the
`test_assembly_chooser` module in commit 91e4e1f.

app-proto/src/components/point.vert

@@ -0,0 +1,24 @@
+#version 300 es
+
+in vec4 position;
+in vec4 color;
+in float highlight;
+in float selected;
+
+out vec4 point_color;
+out float point_highlight;
+out float total_radius;
+
+// camera
+const float focal_slope = 0.3;
+
+void main() {
+    total_radius = 5. + 0.5*selected;
+    
+    float depth = -focal_slope * position.z;
+    gl_Position = vec4(position.xy / depth, 0., 1.);
+    gl_PointSize = 2.*total_radius;
+    
+    point_color = color;
+    point_highlight = highlight;
+}