fix(cli): require installed source for local template hives

The template package resolver should not treat every registered `pr-*`
channel as an installed hive. That made the hive-gate test select the PR
channel even when no local hive/source existed on disk.

Keep the dogfood install-prefix behavior, but only count a local-build
channel as a hive signal when its Aspire package source is a local path
that exists. Arbitrary registered channels without installed packages keep
falling back to the implicit channel.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: radical

src/Aspire.Cli/Templating/TemplateNuGetConfigService.cs

@@ -209,10 +209,10 @@ public async Task<TemplatePackageSelection> ResolveTemplatePackageAsync(Template
         // Honor PR hives only when the caller opts in. Init suppresses this so a developer
         // with stale ~/.aspire/hives/* doesn't get a different template than on a clean machine.
         // PR dogfood installs can discover a matching local-build channel outside the default
-        // hives directory, so also treat an explicit local-build channel as a hive signal.
+        // hives directory, so also treat an installed local-build source as a hive signal.
         var hasPrHives = query.IncludePrHives &&
             (executionContext.GetHiveCount() > 0 ||
-                allChannels.Any(c => c.Type is PackageChannelType.Explicit && VersionHelper.IsLocalBuildChannel(c.Name)));
+                allChannels.Any(static c => c.Type is PackageChannelType.Explicit && HasInstalledLocalBuildPackageSource(c)));
 
         IEnumerable<PackageChannel> channels;
         if (!string.IsNullOrEmpty(query.RequestedChannel))
@@ -296,6 +296,16 @@ await Parallel.ForEachAsync(channels, cancellationToken, async (channel, ct) =>
         return new TemplatePackageSelection(prompted.Package, prompted.Channel);
     }
 
+    private static bool HasInstalledLocalBuildPackageSource(PackageChannel channel)
+    {
+        return VersionHelper.IsLocalBuildChannel(channel.Name) &&
+            channel.Mappings?.Any(static mapping =>
+                mapping.PackageFilter.StartsWith("Aspire", StringComparison.OrdinalIgnoreCase) &&
+                mapping.PackageFilter != PackageMapping.AllPackages &&
+                !UrlHelper.IsHttpUrl(mapping.Source) &&
+                Directory.Exists(mapping.Source)) == true;
+    }
+
     /// <summary>
     /// Installs the resolved Aspire project templates package, generating a temporary NuGet.config from the channel mappings when the channel is explicit.
     /// </summary>