test(desktop): the source-channel handoff fixture answers stable from releases/latest

Since #135847, stable is the latest published GitHub release
(`releases/latest`), not the R2 release-candidates pointer. The fixture still
served only the pointer, so the check reported "No published stable release"
and the test went red on main (the Python-only PR skipped the Desktop lane).

apps/desktop/electron/updater/checkout-source.test.ts

@@ -266,7 +266,12 @@ it('carries each install channel from Python publication checks into the source
       responses.set(`/repos/NousResearch/hermes-agent/commits/${tags[channel]}`, { sha })
     }
 
-    responses.set('/releases/stable/release-candidates.json', { tag: tags.stable, commit: commits[1] })
+    // Stable IS the latest published GitHub release; no R2 record is consulted for it.
+    responses.set('/repos/NousResearch/hermes-agent/releases/latest', {
+      tag_name: tags.stable,
+      draft: false,
+      prerelease: false
+    })
     // The 'main' subscription is a source-branch channel record under the R2 protocol.
     responses.set(
       '/releases/channels/main.json',