⚡ Optimize duplicate detection with IntUnionFind and remove Set overhead

[saurabhsharma2u]

Optimized findNearDuplicates in plugins/core/src/graph/duplicate.ts to improve performance and scalability.

Changes:

• Replaced the generic UnionFind<string> class with a specialized, inline integer-based Union-Find using Uint32Array for parent and Uint8Array for rank.
• Pre-calculated BigInt SimHashes into a BigUint64Array to avoid repeated BigInt() constructor calls and string parsing in the inner loop.
• Removed the checkedPairs Set<string>, which was causing RangeError: Set maximum size exceeded with large datasets (e.g., 20,000 nodes).
• Implemented an implicit connectivity check (find(u) === find(v)) to skip redundant Hamming distance calculations for nodes that are already part of the same connected component.

Performance Impact:

• Stability: Fixed a crash on large inputs (20k nodes) due to Set size limits.
• Speed: Reduced execution time for 20k nodes from infinite (crash) to ~6.3 seconds in benchmarks.
• Memory: Significantly reduced memory usage by eliminating millions of string allocations for edge keys.

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PR created automatically by Jules for task 11828779434289117858 started by @saurabhsharma2u

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[saurabhsharma2u]

Review complete ✅. Huge performance win! I manually rebased this branch to integrate the IntUnionFind optimization cleanly on top of the recent modular refactoring (PR 43). Addressed merge conflicts and ensured tests all pass. Great job reducing memory overhead drastically instead of crashing on large sizes.