test: stabilize pre-tag main validation

The Unix private-endpoint relay regression combines socket authentication, SQLite journaling, attach relay framing, and two protocol requests. Give only that end-to-end case a bounded 30-second allowance so a loaded serial CI runner does not fail its previous 5-second default.

Document the mandatory Desktop release order in BUILD.md: push the candidate to both main branches, wait for validators and the production bundle on that exact SHA, and only then create the annotated tag.

src/agent-daemon/private-endpoint.test.ts

@@ -340,7 +340,8 @@ describe('private endpoint lifecycle', () => {
       await relay
       await endpoint.close()
       events.close()
-    }
+    },
+    30_000
   )
 })