Replace `AlignedBoxWithSlice` with plain `Vec`/`Matrix` where alignment is not needed

[wuw92]

Tracking issue for removing AlignedBoxWithSlice usage where the alignment is not actually needed, identified during the file-centric flow audit (#899).

Discussion

Originating proposal and maintainer confirmation in #899:

• Proposal: Maintenance of diskann-providers #899 (comment)
• Maintainer confirmation (SIMD handles unaligned / arbitrary-length data): Maintenance of diskann-providers #899 (comment)

Scope boundary vs. #907

#907 tracks replacing AlignedBoxWithSlice with diskann-quantization::alloc::Poly for cases that do require alignment (e.g. direct I/O sector-aligned buffers).

This issue tracks the complementary cleanup: callers that use AlignedBoxWithSlice but whose consumers (distance computation through diskann-vector SIMD, or scalar PQ table lookups) don't actually require alignment. These can be replaced with plain Vec / Matrix.

Related PRs

• Replace AlignedBoxWithSlice with plain Vec / Matrix where alignment is unused #955
• Replace AlignedBoxWithSlice with Vec in PQScratch and disk fp vector caches #960