fix(installer): make updates idempotent and harden CI staging

tools/scripts/tests/installer_update_sync.test.js

@@ -0,0 +1,85 @@
+const assert = require("assert");
+const fs = require("fs");
+const os = require("os");
+const path = require("path");
+const { spawnSync } = require("child_process");
+
+const installer = require(path.resolve(__dirname, "..", "..", "bin", "install.js"));
+
+function writeSkill(repoRoot, skillName, content = "# Skill\n") {
+  const skillDir = path.join(repoRoot, "skills", skillName);
+  fs.mkdirSync(skillDir, { recursive: true });
+  fs.writeFileSync(path.join(skillDir, "SKILL.md"), content, "utf8");
+}
+
+function createFakeRepo(rootDir, skills) {
+  fs.mkdirSync(path.join(rootDir, "skills"), { recursive: true });
+  for (const skillName of skills) {
+    writeSkill(rootDir, skillName, `# ${skillName}\n`);
+  }
+}
+
+function readManifestEntries(targetDir) {
+  const manifestPath = path.join(targetDir, ".antigravity-install-manifest.json");
+  const manifest = JSON.parse(fs.readFileSync(manifestPath, "utf8"));
+  return manifest.entries;
+}
+
+const tmpRoot = fs.mkdtempSync(path.join(os.tmpdir(), "installer-update-sync-"));
+
+try {
+  const repoV1 = path.join(tmpRoot, "repo-v1");
+  const repoV2 = path.join(tmpRoot, "repo-v2");
+  const targetDir = path.join(tmpRoot, "target");
+  fs.mkdirSync(targetDir, { recursive: true });
+
+  createFakeRepo(repoV1, ["skill-a", "skill-b"]);
+  createFakeRepo(repoV2, ["skill-a"]);
+
+  installer.installForTarget(repoV1, { name: "Test", path: targetDir });
+  assert.ok(fs.existsSync(path.join(targetDir, "skill-a", "SKILL.md")));
+  assert.ok(fs.existsSync(path.join(targetDir, "skill-b", "SKILL.md")));
+
+  installer.installForTarget(repoV2, { name: "Test", path: targetDir });
+  assert.ok(fs.existsSync(path.join(targetDir, "skill-a", "SKILL.md")));
+  assert.strictEqual(
+    fs.existsSync(path.join(targetDir, "skill-b")),
+    false,
+    "stale managed skill should be pruned during updates",
+  );
+  assert.deepStrictEqual(
+    readManifestEntries(targetDir),
+    ["skill-a"],
+    "install manifest should mirror the latest installed entries",
+  );
+
+  const badTargetPath = path.join(tmpRoot, "bad-target");
+  fs.writeFileSync(badTargetPath, "not-a-directory", "utf8");
+  const badTargetCheck = spawnSync(
+    process.execPath,
+    [
+      "-e",
+      `
+const installer = require(${JSON.stringify(path.resolve(__dirname, "..", "..", "bin", "install.js"))});
+installer.installForTarget(${JSON.stringify(repoV2)}, { name: "BadTarget", path: ${JSON.stringify(badTargetPath)} });
+`,
+    ],
+    {
+      stdio: "pipe",
+      encoding: "utf8",
+    },
+  );
+
+  assert.notStrictEqual(
+    badTargetCheck.status,
+    0,
+    "installer should fail fast when target path exists as a non-directory",
+  );
+  assert.match(
+    `${badTargetCheck.stdout}\n${badTargetCheck.stderr}`,
+    /not a directory/i,
+    "installer should print a clear error for non-directory targets",
+  );
+} finally {
+  fs.rmSync(tmpRoot, { recursive: true, force: true });
+}