Harden update and release tooling

tests/release_scripts.rs

@@ -0,0 +1,20 @@
+#[test]
+fn quiet_update_keeps_prebuilt_enabled_by_default() {
+    let install = include_str!("../install.sh");
+    assert!(install.contains("use_prebuilt=\"${DOSH_USE_PREBUILT:-1}\""));
+    assert!(
+        !install.contains("use_prebuilt=0"),
+        "quiet updates must not force source builds"
+    );
+}
+
+#[test]
+fn release_scripts_skip_stale_artifacts_when_auto_discovering() {
+    let upload = include_str!("../scripts/upload-gitea-release.sh");
+    assert!(upload.contains("skipping $artifact: version"));
+    assert!(upload.contains("expected_version"));
+
+    let publish = include_str!("../scripts/publish-gitea-release.sh");
+    assert!(publish.contains("skipping stale artifact"));
+    assert!(publish.contains("actual=\"$(artifact_version \"$artifact\" || true)\""));
+}