test(fuzz): add C ABI op-sequence fuzzing

[membphis]

Summary

• add a libFuzzer stateful C-ABI op-sequence target that drives parse/get/cursor/object-entry/free flows through exported qjson symbols
• consume returned string/key pointer pairs immediately in the harness so the documented scratch-buffer invalidation contract is respected
• fix and cover root scalar access through FFI cursors, which the new harness exposed during ASAN fuzzing

Test Plan

• make lint
• cargo +nightly fuzz build
• cargo test --release
• cargo test --release --no-default-features
• cargo +nightly fuzz run fuzz_ffi_ops -- -max_total_time=30

Closes #75.

[coderabbitai]

Warning

Review limit reached

@membphis, we couldn't start this review because you've reached your PR review rate limit.

More reviews will be available in 57 minutes and 40 seconds. Learn how PR review limits work.

Your organization has run out of usage credits. Purchase more in the billing tab.

⌛ How to resolve this issue?

After more reviews become available, a review can be triggered using the @coderabbitai review command as a PR comment. Alternatively, push new commits to this PR.

We recommend that you space out your commits to avoid hitting the rate limit.

🚦 How do rate limits work?

CodeRabbit enforces hourly rate limits for each developer per organization.

Our paid plans include higher PR review limits than trial, open-source, and free plans. In all cases, reviews become available again over time. During sustained high-volume PR review activity, CodeRabbit may temporarily slow when the next review becomes available.

Please see our Fair Usage Limits Policy for further information.

ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 6d329d8e-febe-4092-bcbb-4e3166e7a7ee

📥 Commits

Reviewing files that changed from the base of the PR and between 5c4c3c6 and 7d7312c.

📒 Files selected for processing (6)

• fuzz/Cargo.toml
• fuzz/fuzz_targets/fuzz_ffi_ops.rs
• src/cursor.rs
• src/doc.rs
• src/ffi.rs
• tests/ffi_smoke.rs

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch codex/issue-75-ffi-ops-fuzz

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands and usage tips.}