fix(releases): don't drop the prerelease marker when comparing versions

A MinVer dev build on main computes a prerelease of its own guessed next
version (e.g. 2.9.1-alpha.0.14 after tag v2.9.0), which already sorts
above the last tag by numeric core, so the update banner correctly
stays quiet there. But the reduction to a bare numeric core meant a
genuine new release landing at exactly that guessed version (v2.9.1
real) compared equal to the still-running prerelease and the banner
never fired. A prerelease now only loses to a real release of the same
core, not to another prerelease of the same core.

Verified against the live repo: latest published tag is v2.9.0; a
Release build of this worktree (14 commits ahead) reports
AssemblyInformationalVersion 2.9.1-alpha.0.14+<sha>.

src/ClaudeDo.App/Program.cs

@@ -111,7 +111,9 @@ sealed class Program
             var releases = sp.GetRequiredService<IReleaseClient>();
             var informational = Assembly.GetEntryAssembly()?
                 .GetCustomAttribute<AssemblyInformationalVersionAttribute>()?.InformationalVersion;
-            // Strip MinVer build metadata ("+sha") and any prerelease suffix for the update-compare.
+            // Strip MinVer build metadata ("+sha") only — keep the prerelease suffix
+            // (e.g. "-alpha.0.14"), VersionComparer needs it to tell a dev build on
+            // main apart from a tagged release of the same numeric core.
             var version = (informational ?? "0.0.0").Split('+')[0];
             return new UpdateCheckService(releases, version);
         });