Fix MDBX transaction overlaps in CategoryIndex & integrate single transaction

[MithunEndee]

Pull Request

Summary

Integrates the single transaction and resolves MDBX_TXN_OVERLAPPING crashes in CategoryIndex. Updated the indexing methods (add, remove, add_batch) to reuse existing write transactions instead of accidentally opening conflicting nested read transactions.

Type of Change

• Bug fix
• New feature
• Breaking change
• Documentation update
• Refactor / cleanup

Related Issue

Closes #

Checklist

• Code compiles and tests pass
• New tests added where applicable
• Documentation updated if needed
• No unintended breaking changes

[github-actions]

VectorDB Benchmark - Ready To Run

CI Passed ([lint + unit tests] (https://github.com/endee-io/endee/actions/runs/25476601767)) - benchmark options unlocked.

Post one of the command below. Only members with write access can trigger runs.

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Available Modes

Mode	Command	What runs
Dense	/correctness_benchmarking dense	HNSW insert throughput · query P50/P95/P99 · recall@10 · concurrent QPS
Hybrid	/correctness_benchmarking hybrid	Dense + sparse BM25 fusion · same suite + fusion latency overhead

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Infrastructure

Server	Role	Instance
Endee Server	Endee VectorDB — code from this branch	t2.large
Benchmark Server	Benchmark runner	t3a.large

Both servers start on demand and are always terminated after the run — pass or fail.

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How Correctness Benchmarking Works

1. Post /correctness_benchmarking <mode>
2. Endee Server Create  →  this branch's code deployed  →  Endee starts in chosen mode
3. Benchmark Server Create  →  benchmark suite transferred
4. Benchmark Server runs correctness benchmarking against Endee Server
5. Results posted back here  →  pass/fail + full metrics table
6. Both servers terminated   →  always, even on failure

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