fix(releases): strip prerelease and build metadata before version compare

System.Version can't parse SemVer prerelease ("-alpha") or MinVer build
metadata ("+sha") suffixes, so an installed 1.0.2-alpha was treated as
unparseable. Reduce both sides to their numeric core before comparing.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/ClaudeDo.Releases/VersionComparer.cs

@@ -6,13 +6,16 @@ public static class VersionComparer
 {
     public static VersionCompareResult Compare(string latest, string current)
     {
-        var latestTrimmed = (latest ?? "").TrimStart('v', 'V');
+        var unparseable = !Version.TryParse(CoreVersion(latest), out var lv)
-        var currentTrimmed = (current ?? "").TrimStart('v', 'V');
+                        | !Version.TryParse(CoreVersion(current), out var cv);
-
-        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);
     }
+
+    // Reduce a tag/version to its numeric core: drop a leading "v", MinVer build
+    // metadata ("+sha"), and any SemVer prerelease suffix ("-alpha") — none of
+    // which System.Version can parse. So "v1.0.2-alpha+abc" -> "1.0.2".
+    private static string CoreVersion(string value)
+        => (value ?? "").TrimStart('v', 'V').Split('+')[0].Split('-')[0];
 }

tests/ClaudeDo.Releases.Tests/VersionComparerTests.cs

@@ -9,6 +9,14 @@ public class VersionComparerTests
     [InlineData("v0.2.0", "0.1.0", true, false)]
     [InlineData("0.2.0", "v0.1.0", true, false)]
     [InlineData("1.0.0.0", "0.99.99.99", true, false)]
+    // Prerelease and build-metadata suffixes are stripped to the numeric core
+    // before comparing (System.Version can't parse them otherwise).
+    [InlineData("0.2.0-beta", "0.1.0", true, false)]
+    [InlineData("0.2.0", "0.1.0-alpha", true, false)]
+    [InlineData("1.2.0", "1.0.2-alpha", true, false)]                       // real-world: installed 1.0.2-alpha -> 1.2.0
+    [InlineData("v1.0.2-alpha+1c764dae", "1.0.0", true, false)]             // v-prefix + prerelease + build metadata combined
+    [InlineData("1.0.2-alpha+abc", "1.0.2-alpha", false, false)]           // same core -> not newer
+    [InlineData("1.2.0-rc1", "1.2.0", false, false)]                       // prerelease of an already-installed release
     public void Compare_ParseableVersions(string latest, string current, bool expectedNewer, bool expectedUnparseable)
     {
         var result = VersionComparer.Compare(latest, current);
@@ -17,9 +25,8 @@ public class VersionComparerTests
     }
 
     [Theory]
-    [InlineData("0.2.0-beta", "0.1.0")]
-    [InlineData("0.2.0", "0.1.0-alpha")]
     [InlineData("garbage", "0.1.0")]
+    [InlineData("0.2.0", "garbage")]
     [InlineData("", "0.1.0")]
     public void Compare_UnparseableReturnsNotNewer(string latest, string current)
     {