fix(queuefs): preserve SQLite payload bytes

[duyua9]

Summary

• store SQLite QueueFS StoredMessage.data as raw bytes instead of converting through String::from_utf8_lossy
• keep compatibility with existing legacy queue rows whose JSON data field is a string
• add a regression covering non-UTF-8 payload bytes through SQLite peek and dequeue

Validation

• git diff --check
• python3 /Users/ming/.openclaw/skills/github-multi-account-routing/scripts/verify_pr_submission_identity.py --repo volcengine/OpenViking --worktree /Users/ming/code/volcengine/worktrees/openviking-queuefs-sqlite-bytes-duyua9 --account duyua9
• attempted cargo test -p ragfs plugins::queuefs::backend::tests::test_sqlite_backend_preserves_non_utf8_payload_bytes but the local macOS toolchain failed before compiling project code because xcrun cannot load /Library/Developer/CommandLineTools/usr/lib/libxcrun.dylib due to an architecture mismatch (have x86_64, need arm64e).

[github-actions]

PR Reviewer Guide 🔍

Here are some key observations to aid the review process:

⏱️ Estimated effort to review: 2 🔵🔵⚪⚪⚪

🏅 Score: 92

🧪 PR contains tests

🔒 No security concerns identified

✅ No TODO sections

🔀 No multiple PR themes

⚡ No major issues detected

[github-actions]

PR Code Suggestions ✨

No code suggestions found for the PR.