feat: per-platform Chromium versioning and build number support

- Add PLATFORM_CHROMIUM_VERSIONS map (Linux=v145, macOS=v142)
- Add get_chromium_version()/getChromiumVersion() for platform-specific version
- Make auto-update check release assets before offering updates
- Scope version markers per-platform (latest_version_linux-x64)
- Support 5th version segment for hotfix builds (e.g. 145.0.7632.109.2)
- Derive AVAILABLE_PLATFORMS from version map

js/tests/update.test.ts

@@ -1,11 +1,14 @@
-import { describe, it, expect } from "vitest";
+import { describe, it, expect, vi, afterEach } from "vitest";
 import {
   CHROMIUM_VERSION,
+  getChromiumVersion,
   getDownloadUrl,
   getEffectiveVersion,
+  getPlatformTag,
   parseVersion,
   versionNewer,
 } from "../src/config.js";
+import { getLatestChromiumVersion } from "../src/download.js";
 
 describe("version comparison", () => {
   it("parseVersion handles 4-part versions", () => {
@@ -32,13 +35,29 @@ describe("version comparison", () => {
   it("major bump wins over minor", () => {
     expect(versionNewer("143.0.0.0", "142.9.9999.999")).toBe(true);
   });
+
+  it("parseVersion handles 5-part build numbers", () => {
+    expect(parseVersion("145.0.7632.109.2")).toEqual([145, 0, 7632, 109, 2]);
+  });
+
+  it("build bump detected", () => {
+    expect(versionNewer("145.0.7632.109.3", "145.0.7632.109.2")).toBe(true);
+  });
+
+  it("build suffix newer than no suffix", () => {
+    expect(versionNewer("145.0.7632.109.2", "145.0.7632.109")).toBe(true);
+  });
+
+  it("no suffix older than build suffix", () => {
+    expect(versionNewer("145.0.7632.109", "145.0.7632.109.2")).toBe(false);
+  });
 });
 
 describe("download URL", () => {
   it("uses chromium-v prefix and cloakbrowser repo", () => {
     const url = getDownloadUrl();
     expect(url).toContain("cloakbrowser.dev");
-    expect(url).toContain(`chromium-v${CHROMIUM_VERSION}`);
+    expect(url).toContain(`chromium-v${getChromiumVersion()}`);
     expect(url.endsWith(".tar.gz")).toBe(true);
   });
 
@@ -53,9 +72,86 @@ describe("download URL", () => {
   });
 });
 
+describe("latest version (platform-aware)", () => {
+  const platformTarball = `cloakbrowser-${getPlatformTag()}.tar.gz`;
+
+  function makeAssets(platforms: string[]) {
+    return platforms.map((p) => ({ name: `cloakbrowser-${p}.tar.gz` }));
+  }
+
+  function mockFetch(releases: Array<Record<string, unknown>>) {
+    return vi.spyOn(globalThis, "fetch").mockResolvedValue({
+      ok: true,
+      json: async () => releases,
+    } as Response);
+  }
+
+  afterEach(() => {
+    vi.restoreAllMocks();
+  });
+
+  it("returns version when release has platform asset", async () => {
+    mockFetch([
+      {
+        tag_name: "chromium-v145.0.7718.0",
+        draft: false,
+        assets: makeAssets(["linux-x64", "darwin-arm64", "darwin-x64"]),
+      },
+    ]);
+    expect(await getLatestChromiumVersion()).toBe("145.0.7718.0");
+  });
+
+  it("skips release without platform asset", async () => {
+    const spy = mockFetch([
+      {
+        tag_name: "chromium-v145.0.7718.0",
+        draft: false,
+        assets: makeAssets(["linux-x64"]), // Linux only
+      },
+      {
+        tag_name: "chromium-v142.0.7444.175",
+        draft: false,
+        assets: makeAssets(["linux-x64", "darwin-arm64", "darwin-x64"]),
+      },
+    ]);
+    const result = await getLatestChromiumVersion();
+    const tag = getPlatformTag();
+    if (tag === "linux-x64") {
+      expect(result).toBe("145.0.7718.0");
+    } else {
+      expect(result).toBe("142.0.7444.175");
+    }
+  });
+
+  it("returns null when no release has platform asset", async () => {
+    mockFetch([
+      {
+        tag_name: "chromium-v145.0.7718.0",
+        draft: false,
+        assets: [{ name: "cloakbrowser-windows-x64.tar.gz" }],
+      },
+    ]);
+    expect(await getLatestChromiumVersion()).toBeNull();
+  });
+
+  it("skips draft releases", async () => {
+    const all = ["linux-x64", "darwin-arm64", "darwin-x64"];
+    mockFetch([
+      { tag_name: "chromium-v999.0.0.0", draft: true, assets: makeAssets(all) },
+      { tag_name: "chromium-v145.0.7718.0", draft: false, assets: makeAssets(all) },
+    ]);
+    expect(await getLatestChromiumVersion()).toBe("145.0.7718.0");
+  });
+
+  it("returns null on network error", async () => {
+    vi.spyOn(globalThis, "fetch").mockRejectedValue(new Error("timeout"));
+    expect(await getLatestChromiumVersion()).toBeNull();
+  });
+});
+
 describe("effective version", () => {
-  it("returns CHROMIUM_VERSION when no marker exists", () => {
+  it("returns platform version when no marker exists", () => {
     // Default behavior — no marker file in test environment
-    expect(getEffectiveVersion()).toBe(CHROMIUM_VERSION);
+    expect(getEffectiveVersion()).toBe(getChromiumVersion());
   });
 });