chore: import upstream snapshot with attribution

@omniroute/opencode-plugin/tests/disk-snapshot-perms.test.ts

@@ -0,0 +1,66 @@
+/**
+ * Regression test for the disk-snapshot file permissions (release/v3.8.2
+ * review finding C2). The snapshot embeds provider topology + connection
+ * records and lives alongside auth.json (0o600), so it must NOT be readable by
+ * group/other. Before the fix it was written with the default (typically
+ * world-readable 0o644) mode.
+ */
+
+import test from "node:test";
+import assert from "node:assert/strict";
+import fs from "node:fs";
+import os from "node:os";
+import path from "node:path";
+
+import {
+  defaultDiskSnapshotWriter,
+  diskSnapshotPath,
+  type OmniRouteFetchCacheEntry,
+} from "../src/index.js";
+
+function makeEntry(): Omit<OmniRouteFetchCacheEntry, "expiresAt"> {
+  return {
+    rawModels: [],
+    rawCombos: [],
+    rawEnrichment: new Map(),
+    rawCompressionCombos: [],
+    rawConnections: [],
+  };
+}
+
+test("defaultDiskSnapshotWriter writes an owner-only (no group/other) snapshot", async (t) => {
+  // POSIX-only assertion; Windows does not honor numeric file modes.
+  if (process.platform === "win32") {
+    t.skip("file mode semantics are POSIX-only");
+    return;
+  }
+
+  const tmp = fs.mkdtempSync(path.join(os.tmpdir(), "omniroute-disk-perms-"));
+  const prevDataDir = process.env.OPENCODE_DATA_DIR;
+  process.env.OPENCODE_DATA_DIR = tmp;
+
+  try {
+    await defaultDiskSnapshotWriter("perm-test", makeEntry());
+
+    const file = diskSnapshotPath("perm-test");
+    assert.ok(fs.existsSync(file), "snapshot file should be written");
+
+    const fileMode = fs.statSync(file).mode & 0o777;
+    assert.equal(
+      fileMode & 0o077,
+      0,
+      `snapshot must not be group/other accessible (got ${fileMode.toString(8)})`
+    );
+
+    const dirMode = fs.statSync(path.dirname(file)).mode & 0o777;
+    assert.equal(
+      dirMode & 0o077,
+      0,
+      `plugins dir must not be group/other accessible (got ${dirMode.toString(8)})`
+    );
+  } finally {
+    if (prevDataDir === undefined) delete process.env.OPENCODE_DATA_DIR;
+    else process.env.OPENCODE_DATA_DIR = prevDataDir;
+    fs.rmSync(tmp, { recursive: true, force: true });
+  }
+});