feat(releases): add VersionComparer

src/ClaudeDo.Releases/VersionComparer.cs

@@ -0,0 +1,18 @@
+namespace ClaudeDo.Releases;
+
+public readonly record struct VersionCompareResult(bool IsNewer, bool Unparseable);
+
+public static class VersionComparer
+{
+    public static VersionCompareResult Compare(string latest, string current)
+    {
+        var latestTrimmed = (latest ?? "").TrimStart('v', 'V');
+        var currentTrimmed = (current ?? "").TrimStart('v', 'V');
+
+        var unparseable = !Version.TryParse(latestTrimmed, out var lv)
+                        | !Version.TryParse(currentTrimmed, out var cv);
+
+        if (unparseable) return new VersionCompareResult(false, true);
+        return new VersionCompareResult(lv > cv, false);
+    }
+}