fix(ci): migrate to the latest macOS runners (#8335)

* fix(ci): replace retiring macOS 14 runners

Use the supported macOS 15 ARM64 image before the November 2 retirement. Keep the Intel release runner and existing test/build/release commands unchanged.

* fix(ci): use the latest macOS runner images

.github/workflows/ci.yml

@@ -281,10 +281,10 @@ jobs:
   # otherwise has no server-test coverage. Scoped to the observer/watcher suites to
   # bound runtime.
   server-tests-macos:
-    name: server-tests (macos-14, file observation)
+    name: server-tests (macos-latest, file observation)
     needs: changes
     if: ${{ !cancelled() && (needs.changes.outputs.full != 'false' || needs.changes.outputs.server != 'false') }}
-    runs-on: macos-14
+    runs-on: macos-latest
     steps:
       - uses: actions/checkout@v4
 

.github/workflows/desktop-release.yml

@@ -100,10 +100,10 @@ jobs:
       fail-fast: false
       matrix:
         include:
-          - runner: macos-14
+          - runner: macos-latest
             electron_arch: arm64
             node_heap_mb: 4096
-          - runner: macos-15-intel
+          - runner: macos-26-intel
             electron_arch: x64
             node_heap_mb: 8192
     permissions:

.github/workflows/nix.yml

@@ -101,7 +101,7 @@ jobs:
         run: nix build .#desktop -o result-desktop
 
   build-desktop-darwin:
-    runs-on: macos-14
+    runs-on: macos-latest
     steps:
       - uses: actions/checkout@v4
 

scripts/ci-workflow.test.mjs

@@ -24,7 +24,10 @@ const gatedCiJobs = new Map([
     "server-integration-windows",
     { name: "server-integration (windows-latest)", contract: "server" },
   ],
-  ["server-tests-macos", { name: "server-tests (macos-14, file observation)", contract: "server" }],
+  [
+    "server-tests-macos",
+    { name: "server-tests (macos-latest, file observation)", contract: "server" },
+  ],
   ["desktop-tests-ubuntu", { name: "desktop-tests (ubuntu-latest)", contract: "desktop" }],
   ["desktop-tests-windows", { name: "desktop-tests (windows-latest)", contract: "desktop" }],
   ["app-tests", { name: "app-tests", contract: "app" }],
@@ -649,3 +652,30 @@ process.exit(code);
     });
   }
 });
+
+// GitHub retires macOS 14 on 2026-11-02; brownouts already reject these jobs.
+test("workflows avoid retired macOS 14 runners", () => {
+  for (const path of filesUnder(".github/workflows", (candidate) => /\.ya?ml$/.test(candidate))) {
+    assert.doesNotMatch(
+      readFileSync(new URL(path, repoRoot), "utf8"),
+      /macos-14(?:-large|-xlarge)?\b/,
+      path,
+    );
+  }
+});
+
+test("macOS jobs use latest runners while preserving release architectures", () => {
+  for (const [workflow, jobId] of [
+    [ciWorkflowPath, "server-tests-macos"],
+    [nixWorkflowPath, "build-desktop-darwin"],
+  ]) {
+    assert.match(
+      jobBlocks(readFileSync(workflow, "utf8")).get(jobId).join("\n"),
+      /^    runs-on: macos-latest$/m,
+    );
+  }
+  const release = readFileSync(new URL(".github/workflows/desktop-release.yml", repoRoot), "utf8");
+  assert.match(release, /runner: macos-latest\n\s+electron_arch: arm64/);
+  // GitHub has no standard macos-latest-intel alias; use the newest Intel image.
+  assert.match(release, /runner: macos-26-intel\n\s+electron_arch: x64/);
+});