refactor(posts): move post-processor projects under Posts/

Group the Cincinnati and GravographIS plugin projects in a Posts/
folder so new machine posts have one home. Project names, namespaces,
and the runtime Posts/ deploy target are unchanged; only relative
paths in the solution and project references move.

Posts/OpenNest.Posts.Cincinnati/CoordinateFormatter.cs

@@ -0,0 +1,25 @@
+namespace OpenNest.Posts.Cincinnati
+{
+    public sealed class CoordinateFormatter
+    {
+        private readonly int _accuracy;
+        private readonly string _format;
+
+        public CoordinateFormatter(int accuracy)
+        {
+            _accuracy = accuracy;
+            _format = "0." + new string('#', accuracy);
+        }
+
+        public string FormatCoord(double value)
+        {
+            return System
+                .Math.Round(value, _accuracy)
+                .ToString(_format, System.Globalization.CultureInfo.InvariantCulture);
+        }
+
+        public static string Comment(string text) => $"( {text} )";
+
+        public static string InlineComment(string text) => $"({text})";
+    }
+}