test(installer): pin 'unparseable version = Config' behavior + document IsNewer limits

src/ClaudeDo.Installer/Core/InstallModeDetector.cs

@@ -32,6 +32,13 @@ public sealed class InstallModeDetector
         return new DetectedState(InstallerMode.Config, manifest, release, latestVersion);
     }
 
+    /// <summary>
+    /// Returns true only when both versions parse as System.Version (major.minor[.build[.revision]])
+    /// AND latest &gt; current. Semver pre-release tags like "0.2.0-beta" fail to parse and are
+    /// treated as "not newer" — the user drops into Config mode with no update offered.
+    /// This is deliberate: offering an update we can't compare is worse than silently skipping it.
+    /// If the project starts shipping pre-release tags, revisit this.
+    /// </summary>
     private static bool IsNewer(string latest, string current)
     {
         if (!Version.TryParse(latest, out var lv)) return false;