fix(release): a snap built in a clone of its own is packed inside it, then moved into the release's folder

snapcraft packs nowhere outside the project it builds, so Todo 0.1.0's release stopped
after its snap was built ("Cannot create packages outside of the project tree").

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

test/release/app_release_test.dart

@@ -167,6 +167,22 @@ void main() {
       );
     });
 
+    test('is packed inside its clone, as snapcraft packs nowhere outside the '
+        "project, and Learn's into the release's folder", () {
+      expect(
+        snap.packPath(home: '/home/someone', root: '/repo', out: 'build/x'),
+        '/home/someone/.cache/halkyon-release/snap/halkyon-todo',
+      );
+      expect(
+        learnRelease.snap!.packPath(
+          home: '/home/someone',
+          root: '/repo',
+          out: 'build/x',
+        ),
+        '/repo/build/x',
+      );
+    });
+
     test('names the snap and the part the release tool takes', () {
       expect(recipe, contains('name: ${snap.name}\n'));
       expect(recipe, contains('\n  ${snap.part}:\n    after: [flutter]\n'));