Add CSR matrix builder with deduplication and optimize assembly with binary search

[Copilot]

Adds support for building CSR matrices from COO triplets with automatic deduplication, and optimizes the Assemble function from O(n) to O(log n) per lookup.

Changes

New cCSRMatrixBuilder class (include/CSRMatrixBuilder.h)

• Builds CSR matrices from triplets with configurable duplicate handling (accumulate or overwrite)
• Handles unsorted input, sparse patterns, out-of-range entries
• Uses robust hash combining (boost-style) to minimize collisions

Performance optimization (include/CSRComm.h)

• Replaced linear search with binary search in CSRComm::Assemble
• Significant speedup for rows with many columns (O(log n) vs O(n))

Utility functions

• BuildCSRFromTriplets(): convenience wrapper for one-step construction
• ValidateCSRMatrix(): checks row pointer consistency, column sorting, bounds

Example Usage

// Build from unsorted triplets with automatic deduplication
cCSRMatrixBuilder<double> builder;
builder.AddEntry(0, 0, 1.0);
builder.AddEntry(0, 0, 2.0);  // Duplicate - will accumulate
builder.AddEntry(1, 1, 3.0);

auto matrix = builder.Build(0, 2, 2);
// Result: (0,0) = 3.0, (1,1) = 3.0

// Or use convenience function
std::vector<cTriplet<double>> triplets = {...};
auto matrix = BuildCSRFromTriplets(triplets, 0, rows, cols);

Testing

Added 31 test cases covering:

• Duplicate accumulation (same element multiple times)
• Edge cases: empty matrices, single elements, all duplicates
• Binary search correctness: first/middle/last column, large rows (1000+ columns)
• Row range subsets, unsorted input, validation edge cases

Warning

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Original prompt

新增功能：CSR 矩阵构建过程中，同一进程内提供了重复元素时，要支持自动去重，新增对应的测试用例，并调试通过。此外，考虑更多类似的边缘场景处理，增加相应的测试用例。然后完成 TODO 中的性能优化，并保证测试通过。如果你有更多想添加的合理功能点，也请新增并验证通过。

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