fix: harden reproducible checkout races

scripts/install-hooks.test.mjs

@@ -54,7 +54,7 @@ test('an interrupted install quarantines the partial active hook set and fails l
   );
 
   assert.equal(await exists(path.join(root, '.husky', '_')), false);
-  assert.equal(restoredHooksPath, null);
+  assert.equal(restoredHooksPath, 'not-called');
   const quarantined = await readdir(quarantineRoot);
   assert.equal(quarantined.length, 1);
 });
@@ -138,6 +138,38 @@ test('a competing successful installer is not removed by the losing process', as
   assert.equal(restored, false);
 });
 
+test("a competing installer that replaces this installer's active set is preserved", async () => {
+  const root = await fixture('concurrent-after-rename');
+  const active = path.join(root, '.husky', '_');
+  const activeShim = path.join(active, 'h');
+  let restored = false;
+
+  await assert.rejects(
+    installHooks({
+      root,
+      quarantineRoot: path.join(fixtureRoot, 'concurrent-after-rename-quarantine'),
+      runHusky: async (stagingHooks) => {
+        await mkdir(path.join(stagingHooks, '_'), { recursive: true });
+        await writeFile(path.join(stagingHooks, '_', 'h'), 'ours');
+      },
+      activateHooks: async () => {
+        await rm(active, { recursive: true, force: true });
+        await mkdir(active, { recursive: true });
+        await writeFile(activeShim, 'peer');
+        throw new Error('our activation lost to peer');
+      },
+      readHooksPath: async () => null,
+      restoreHooksPath: async () => {
+        restored = true;
+      },
+    }),
+    /Hook installation failed/,
+  );
+
+  assert.equal(await readFile(activeShim, 'utf8'), 'peer');
+  assert.equal(restored, false);
+});
+
 test('an explicit interactive HUSKY=0 opt-out preserves existing hooks without running installer', async () => {
   const root = await fixture('disabled');
   const activeShim = path.join(root, '.husky', '_', 'h');