feat: add GraphBLAS serialization primitives

[AviAvni]

Summary

Core serialization infrastructure that all higher-level RDB persistence code depends on. Extracted from #359 (PR 4 of the split).

• New serialization.rs module (~219 lines): Writer/Reader traits abstracting serialization sinks/sources, versioned Encode<V>/Decode<V> traits, si_type type-tag constants (matching C FalkorDB format), EncodeState/PayloadEntry for chunked virtual-key encoding, and RoaringTreemap encode/decode for deleted entity bitmaps
• Matrix encode/decode (~268 lines added): Encode<19>/Decode<19> for SparseMatrix using GxB_Container export/import, plus SparseMatrixIterator
• Vector encode/decode (~229 lines added): Encode<19>/Decode<19> for SparseVector using container export/import, plus SparseVectorIterator
• Tensor encode/decode (~148 lines added): Encode<19>/Decode<19> looping over inner matrices
• VersionedMatrix encode/decode (~72 lines added): Delegates to underlying matrix
• Dependencies: roaring and thin-vec added to root Cargo.toml

Test plan

• cargo check passes
• cargo fmt --all -- --check passes
• CI build and test pipeline passes
• Verify no regressions in existing unit tests (cargo test -p graph)

[coderabbitai]

Warning

Rate limit exceeded

@AviAvni has exceeded the limit for the number of commits that can be reviewed per hour. Please wait 24 minutes and 3 seconds before requesting another review.

Your organization is not enrolled in usage-based pricing. Contact your admin to enable usage-based pricing to continue reviews beyond the rate limit, or try again in 24 minutes and 3 seconds.

⌛ How to resolve this issue?

After the wait time has elapsed, 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 have higher rate limits than the trial, open-source and free plans. In all cases, we re-allow further reviews after a brief timeout.

Please see our FAQ for further information.

ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: b8a59c2f-3b44-4849-9ec4-53ab518d2600

📥 Commits

Reviewing files that changed from the base of the PR and between b5de7b2 and b464eb2.

⛔ Files ignored due to path filters (1)

• Cargo.lock is excluded by !**/*.lock

📒 Files selected for processing (7)

• Cargo.toml
• graph/src/graph/graphblas/matrix.rs
• graph/src/graph/graphblas/mod.rs
• graph/src/graph/graphblas/serialization.rs
• graph/src/graph/graphblas/tensor.rs
• graph/src/graph/graphblas/vector.rs
• graph/src/graph/graphblas/versioned_matrix.rs

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch graphblas-serialization

---

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.}

[codecov]

Codecov Report

❌ Patch coverage is 2.29645% with 468 lines in your changes missing coverage. Please review.
✅ Project coverage is 84.14%. Comparing base (b5de7b2) to head (b464eb2).
⚠️ Report is 6 commits behind head on main.

Files with missing lines	Patch %	Lines
graph/src/graph/graphblas/vector.rs	0.00%	142 Missing ⚠️
graph/src/graph/graphblas/matrix.rs	8.19%	112 Missing ⚠️
graph/src/graph/graphblas/tensor.rs	1.04%	95 Missing ⚠️
graph/src/graph/graphblas/serialization.rs	0.00%	88 Missing ⚠️
graph/src/graph/graphblas/versioned_matrix.rs	0.00%	31 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #372      +/-   ##
==========================================
- Coverage   85.50%   84.14%   -1.37%     
==========================================
  Files         109      110       +1     
  Lines       28477    28954     +477     
==========================================
+ Hits        24350    24362      +12     
- Misses       4127     4592     +465     

Flag	Coverage Δ
fuzz	42.20% <2.08%> (-0.20%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.