fix(security): restore .env/auth.json/state.db with 0600 perms

`hermes import` was creating secret files with the process umask
(typically 0644) instead of 0600. zipfile.open() does not honor the
Unix mode bits stored in zip member external_attr; the restore loop
used open(target, "wb") which always falls back to umask.

Threat: silent privilege downgrade after a routine restore on
multi-user systems (shared dev boxes, CI runners, jump hosts) — any
local user could read API keys and OAuth tokens from ~/.hermes/.

Fix mirrors the convention already used at file creation
(hermes_cli/auth.py: stat.S_IRUSR | stat.S_IWUSR for auth.json).
The quick-snapshot restore path (restore_quick_snapshot) is
unaffected — it uses shutil.copy2 which preserves perms via
copystat().

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

tests/hermes_cli/test_backup.py

@@ -471,6 +471,32 @@ class TestImport:
         with pytest.raises(SystemExit):
             run_import(args)
 
+    @pytest.mark.skipif(os.name != "posix", reason="POSIX file permissions only")
+    def test_restores_secret_files_with_0600_perms(self, tmp_path, monkeypatch):
+        """Secret files must end up at 0600 after restore (zipfile drops mode bits)."""
+        hermes_home = tmp_path / ".hermes"
+        hermes_home.mkdir()
+        monkeypatch.setenv("HERMES_HOME", str(hermes_home))
+        monkeypatch.setattr(Path, "home", lambda: tmp_path)
+
+        zip_path = tmp_path / "backup.zip"
+        self._make_backup_zip(zip_path, {
+            "config.yaml": "model: openrouter\n",
+            ".env": "OPENROUTER_API_KEY=sk-secret\n",
+            "auth.json": '{"providers": {"nous": "token"}}',
+            "state.db": b"SQLite format 3\x00",
+            "profiles/coder/.env": "ANTHROPIC_API_KEY=sk-ant-secret\n",
+        })
+
+        args = Namespace(zipfile=str(zip_path), force=True)
+
+        from hermes_cli.backup import run_import
+        run_import(args)
+
+        for rel in (".env", "auth.json", "state.db", "profiles/coder/.env"):
+            mode = (hermes_home / rel).stat().st_mode & 0o777
+            assert mode == 0o600, f"{rel} restored with mode {oct(mode)}, expected 0o600"
+
 
 # ---------------------------------------------------------------------------
 # Round-trip test