feat: add LoongArch preview download to the website

The Chinese Linux download card now includes a LoongArch processor option and fixes its package type to DEB. It reads a separate strictly validated OSS preview index, while the formal six-target release index and English GitHub downloads remain unchanged.

The page keeps three symmetric platform cards, disables only the LoongArch selection when its index is unavailable, and labels the package as unverified on real LoongArch hardware.

Release note: 官网 Linux 下载新增龙芯 LoongArch 处理器选项，选择后提供独立 DEB 预览包；正式下载与更新索引保持不变。

sites/scripts/release-index.test.mjs

@@ -9,7 +9,10 @@ const { test } = process.env.VITEST
 const source = await readFile(path.resolve("sites/release-index.js"), "utf8");
 const context = vm.createContext({ URL, window: {} });
 vm.runInContext(source, context, { filename: "release-index.js" });
-const { validateReleaseIndex } = context.window.GoodBuddyReleaseIndex;
+const {
+  validateReleaseIndex,
+  validateLoongArchPreviewIndex,
+} = context.window.GoodBuddyReleaseIndex;
 
 const definitions = [
   ["windows", "x64", ["nsis", "portable"]],
@@ -90,6 +93,36 @@ const expectRejected = (mutate) => {
   assert.throws(() => validateReleaseIndex(index));
 };
 
+const validLoongArchPreviewIndex = () => {
+  const goodBuddyVersion = "1.2.3";
+  const previewBase =
+    `https://goodbuddy.oss-cn-beijing.aliyuncs.com/releases/loongarch-preview/v${goodBuddyVersion}/`;
+  const name =
+    `GoodBuddy-${goodBuddyVersion}-linux-loong64-preview.deb`;
+  return {
+    formatVersion: 1,
+    product: "GoodBuddy LoongArch Preview",
+    goodBuddyVersion,
+    previewVersion: `${goodBuddyVersion}-loong64-preview.1`,
+    architecture: "loong64",
+    format: "deb",
+    artifact: {
+      name,
+      size: 186_000_000,
+      sha256: "a".repeat(64),
+      url: new URL(encodeURIComponent(name), previewBase).href,
+    },
+    manifestUrl: new URL("preview-manifest.json", previewBase).href,
+    checksumUrl: new URL("SHA256SUMS", previewBase).href,
+  };
+};
+
+const expectLoongArchPreviewRejected = (mutate) => {
+  const index = validLoongArchPreviewIndex();
+  mutate(index);
+  assert.throws(() => validateLoongArchPreviewIndex(index));
+};
+
 test("accepts the canonical stable six-target release index", () => {
   const index = validIndex();
   assert.equal(validateReleaseIndex(index), index);
@@ -204,3 +237,49 @@ test("requires exact checksum and GitHub fallback URLs", () => {
     index.fallbackUrl = "https://github.com/mesalogo/goodbuddy/releases";
   });
 });
+
+test("accepts the isolated immutable LoongArch preview index", () => {
+  const index = validLoongArchPreviewIndex();
+  assert.equal(validateLoongArchPreviewIndex(index), index);
+});
+
+test("binds the LoongArch preview to its stable version and exact OSS prefix", () => {
+  for (const version of ["v1.2.3", "1.2.3-rc.1", "1.2"]) {
+    expectLoongArchPreviewRejected((index) => {
+      index.goodBuddyVersion = version;
+    });
+  }
+  expectLoongArchPreviewRejected((index) => {
+    index.previewVersion = "1.2.3-loong64-preview.0";
+  });
+  expectLoongArchPreviewRejected((index) => {
+    index.artifact.url = index.artifact.url.replace(
+      "/releases/loongarch-preview/v1.2.3/",
+      "/releases/v1.2.3/",
+    );
+  });
+  expectLoongArchPreviewRejected((index) => {
+    index.manifestUrl += "?download=1";
+  });
+  expectLoongArchPreviewRejected((index) => {
+    index.unexpected = true;
+  });
+});
+
+test("requires one canonical LoongArch DEB with bounded metadata", () => {
+  expectLoongArchPreviewRejected((index) => {
+    index.architecture = "arm64";
+  });
+  expectLoongArchPreviewRejected((index) => {
+    index.format = "rpm";
+  });
+  expectLoongArchPreviewRejected((index) => {
+    index.artifact.name = "GoodBuddy-1.2.3-linux-loong64.deb";
+  });
+  expectLoongArchPreviewRejected((index) => {
+    index.artifact.size = 0;
+  });
+  expectLoongArchPreviewRejected((index) => {
+    index.artifact.sha256 = "A".repeat(64);
+  });
+});