fix sync reliability and runtime handling

tests/secure-files.test.ts

@@ -1,5 +1,5 @@
 import { describe, expect, test } from "bun:test";
-import { mkdtempSync, rmSync } from "node:fs";
+import { mkdirSync, mkdtempSync, rmSync, writeFileSync } from "node:fs";
 import { join } from "node:path";
 import { withExclusiveFileLock } from "../src/storage/secure-files.js";
 
@@ -11,4 +11,13 @@ describe("file locks", () => {
     await expect(withExclusiveFileLock(path, async () => "second")).resolves.toBe("second");
     rmSync(directory, { recursive: true, force: true });
   });
+
+  test("reclaims a lock whose owner process is gone", async () => {
+    const directory = mkdtempSync(join(process.env.TMPDIR ?? "/tmp", "miband-lock-stale-"));
+    const path = join(directory, "sync.lock");
+    mkdirSync(`${path}.d`);
+    writeFileSync(join(`${path}.d`, "owner"), "pid=2147483647 time=0\n");
+    await expect(withExclusiveFileLock(path, async () => "reclaimed")).resolves.toBe("reclaimed");
+    rmSync(directory, { recursive: true, force: true });
+  });
 });