feat: add multi-source downloads with automatic fallback

- support GitHub, GitCode, gh-proxy, and ghfast sources
- automatically try other sources when version checks fail
- persist the working fallback source and sync the UI immediately
- update translations, configuration migration, and source tests

src-tauri/src/tests/app_settings.rs

@@ -18,6 +18,7 @@ fn gui_field_edit_preserves_comments_and_unknown_configuration() {
         auth_dir: path_to_string(&home.join("custom-auth")),
         management_secret_key: "custom-secret".to_string(),
         usage_statistics_enabled: false,
+        download_source: VersionDownloadSource::Gitcode,
         prefer_gitcode_downloads: true,
         ..GuiConfigFile::default()
     };
@@ -32,6 +33,7 @@ fn gui_field_edit_preserves_comments_and_unknown_configuration() {
     assert!(content.contains("silent-start = true"));
     assert!(content.contains("management-secret-key = \"custom-secret\""));
     assert!(content.contains("usage-statistics-enabled = false"));
+    assert!(content.contains("download-source = \"gitcode\""));
     assert!(content.contains("prefer-gitcode-downloads = true"));
     assert!(!content.contains("codex-session-repair-on-launch"));
     assert!(!content.contains("claude-code-working-directory"));
@@ -91,6 +93,7 @@ fn gui_config_defaults_are_stable() {
     assert!(content.contains("management-secret-key = \"\""));
     assert!(content.contains("plugins-enabled = false"));
     assert!(content.contains("routing-strategy = \"round-robin\""));
+    assert!(content.contains("download-source = \"github\""));
     assert!(content.contains("prefer-gitcode-downloads = false"));
     assert!(content.contains("request-retry = 3"));
     assert!(content.contains("max-retry-credentials = 0"));

src-tauri/src/tests/app_update.rs

@@ -212,13 +212,42 @@ fn portable_update_download_order_respects_gitcode_preference() {
         &filename,
     )];
 
-    let github_first = portable_update_download_urls(&asset, false);
-    assert_eq!(update_download_source_name(github_first[0]), "GitHub");
-    assert_eq!(update_download_source_name(github_first[1]), "GitCode");
+    let github_first = portable_update_download_urls(&asset, VersionDownloadSource::Github);
+    assert_eq!(update_download_source_name(&github_first[0]), "GitHub");
+    assert_eq!(update_download_source_name(&github_first[1]), "GitCode");
 
-    let gitcode_first = portable_update_download_urls(&asset, true);
-    assert_eq!(update_download_source_name(gitcode_first[0]), "GitCode");
-    assert_eq!(update_download_source_name(gitcode_first[1]), "GitHub");
+    let gitcode_first = portable_update_download_urls(&asset, VersionDownloadSource::Gitcode);
+    assert_eq!(update_download_source_name(&gitcode_first[0]), "GitCode");
+    assert_eq!(update_download_source_name(&gitcode_first[1]), "GitHub");
+
+    let mirror_first = portable_update_download_urls(&asset, VersionDownloadSource::GhProxy);
+    assert_eq!(
+        update_download_source_name(&mirror_first[0]),
+        "gh-proxy.com"
+    );
+    assert_eq!(update_download_source_name(&mirror_first[1]), "GitHub");
+    assert_eq!(update_download_source_name(&mirror_first[2]), "GitCode");
+}
+
+#[test]
+fn version_detection_candidates_try_every_available_source_once() {
+    assert_eq!(
+        version_download_source_candidates(VersionDownloadSource::GhFast, true),
+        [
+            VersionDownloadSource::GhFast,
+            VersionDownloadSource::Github,
+            VersionDownloadSource::Gitcode,
+            VersionDownloadSource::GhProxy,
+        ]
+    );
+    assert_eq!(
+        version_download_source_candidates(VersionDownloadSource::Gitcode, false),
+        [
+            VersionDownloadSource::Github,
+            VersionDownloadSource::GhProxy,
+            VersionDownloadSource::GhFast,
+        ]
+    );
 }
 
 #[test]
@@ -592,7 +621,11 @@ fn synthetic_release_uses_official_asset_names_and_urls() {
 #[test]
 fn synthetic_core_release_uses_gitcode_as_download_fallback() {
     let repository = "lzt404/CLIProxyAPI";
-    let release = release_from_tag_for_repositories("7.2.80", Some(repository), false);
+    let release = release_from_tag_for_repositories(
+        "7.2.80",
+        Some(repository),
+        VersionDownloadSource::Github,
+    );
     let platform = CorePlatform {
         os: "windows".to_string(),
         arch: "x86_64".to_string(),
@@ -634,6 +667,36 @@ fn gitcode_discovered_core_release_downloads_from_gitcode_first() {
     );
 }
 
+#[test]
+fn github_proxy_core_release_uses_proxy_then_official_and_gitcode() {
+    let release = release_from_tag_for_repositories(
+        "v7.2.80",
+        Some("lzt404/CLIProxyAPI"),
+        VersionDownloadSource::GhFast,
+    );
+    let platform = CorePlatform {
+        os: "windows".to_string(),
+        arch: "x86_64".to_string(),
+        asset_os: "windows".to_string(),
+        asset_arch: "amd64".to_string(),
+        archive_kind: "zip".to_string(),
+    };
+    let asset = select_release_asset(&release, &platform).unwrap();
+
+    assert_eq!(
+        core_download_source_name(&asset.browser_download_url),
+        "ghfast.top"
+    );
+    assert_eq!(
+        core_download_source_name(&asset.fallback_download_urls[0]),
+        "GitHub"
+    );
+    assert_eq!(
+        core_download_source_name(&asset.fallback_download_urls[1]),
+        "GitCode"
+    );
+}
+
 #[test]
 fn release_asset_names_cover_the_six_supported_gui_targets() {
     let targets = [

src-tauri/src/tests/core_config.rs

@@ -1039,6 +1039,7 @@ fn startup_preserves_all_user_owned_yaml_and_only_applies_gui_managed_values() {
         plugins_enabled: true,
         routing_strategy: "fill-first".to_string(),
         proxy_url: "socks5://127.0.0.1:7890".to_string(),
+        download_source: VersionDownloadSource::Github,
         prefer_gitcode_downloads: false,
         routing_session_affinity: true,
         routing_session_affinity_ttl: "1h".to_string(),