feat(releases): add SelfUpdater installer-asset matching

src/ClaudeDo.Releases/SelfUpdateResult.cs

@@ -0,0 +1,3 @@
+namespace ClaudeDo.Releases;
+
+public sealed record InstallerAssetMatch(ReleaseAsset Asset, string Version);

src/ClaudeDo.Releases/SelfUpdater.cs

@@ -0,0 +1,22 @@
+using System.Text.RegularExpressions;
+
+namespace ClaudeDo.Releases;
+
+public static partial class SelfUpdater
+{
+    [GeneratedRegex(@"^ClaudeDo\.Installer-(?<version>[\d\.]+)\.exe$", RegexOptions.IgnoreCase)]
+    private static partial Regex InstallerAssetRegex();
+
+    public static InstallerAssetMatch? FindInstallerAsset(IEnumerable<ReleaseAsset> assets)
+    {
+        foreach (var asset in assets)
+        {
+            var m = InstallerAssetRegex().Match(asset.Name);
+            if (m.Success)
+            {
+                return new InstallerAssetMatch(asset, m.Groups["version"].Value);
+            }
+        }
+        return null;
+    }
+}