Remove AsThreadPool generic trait; take &RayonThreadPool directly

[Copilot]

• Remove AsThreadPool generic trait, replace with direct &RayonThreadPool parameters
• Update all callers across workspace (18 files, 4 crates)
• Merge latest main to resolve conflict (accepted main's deletion of normalizing_util.rs)
• Verified: cargo check --workspace --all-targets passes
• Verified: cargo clippy --workspace --all-targets -- -D warnings passes

[codecov-commenter]

Codecov Report

❌ Patch coverage is 93.42105% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 89.34%. Comparing base (de98ea6) to head (b54ae16).

Files with missing lines	Patch %	Lines
diskann-tools/src/utils/build_pq.rs	0.00%	4 Missing ⚠️
diskann-disk/src/build/builder/quantizer.rs	75.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #906   +/-   ##
=======================================
  Coverage   89.34%   89.34%           
=======================================
  Files         444      444           
  Lines       83986    83913   -73     
=======================================
- Hits        75036    74971   -65     
+ Misses       8950     8942    -8     

Flag	Coverage Δ
miri	89.34% <93.42%> (+<0.01%)	⬆️
unittests	89.18% <93.42%> (+<0.01%)	⬆️

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

Files with missing lines	Coverage Δ
diskann-benchmark/src/backend/index/product.rs	100.00% <ø> (ø)
diskann-disk/src/build/builder/build.rs	94.16% <100.00%> (ø)
diskann-disk/src/build/builder/core.rs	95.25% <100.00%> (ø)
diskann-disk/src/storage/quant/generator.rs	92.67% <100.00%> (-0.06%)	⬇️
diskann-disk/src/storage/quant/pq/pq_generation.rs	93.22% <100.00%> (-0.12%)	⬇️
diskann-disk/src/utils/partition.rs	92.51% <100.00%> (-0.04%)	⬇️
diskann-providers/src/index/diskann_async.rs	96.40% <100.00%> (+0.02%)	⬆️
diskann-providers/src/index/wrapped_async.rs	46.17% <100.00%> (+0.31%)	⬆️
.../src/model/graph/provider/async_/debug_provider.rs	84.99% <100.00%> (+0.05%)	⬆️
diskann-providers/src/model/pq/pq_construction.rs	92.03% <100.00%> (-0.12%)	⬇️
... and 6 more

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[Copilot]

Pull request overview

This PR removes the AsThreadPool abstraction and updates the workspace to pass &RayonThreadPool explicitly, simplifying thread-pool handling across PQ training, k-means utilities, disk build workflows, and benchmarks.

Changes:

• Removed AsThreadPool and the forward_threadpool macro; APIs now take &RayonThreadPool directly.
• Updated PQ/k-means/math utilities and all call sites (including tests) to create and pass a RayonThreadPool reference.
• Adjusted generic signatures in PQ construction functions to drop the former thread-pool type parameter.

Reviewed changes

Copilot reviewed 18 out of 18 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
diskann-tools/src/utils/build_pq.rs	Creates a thread pool once and passes &RayonThreadPool into PQ pivot/data generation.
diskann-providers/src/utils/rayon_util.rs	Removes AsThreadPool + macro; keeps RayonThreadPool helpers and in-pool parallel iterator extensions.
diskann-providers/src/utils/mod.rs	Stops re-exporting removed thread-pool abstractions/utilities.
diskann-providers/src/utils/math_util.rs	Updates math helpers to accept &RayonThreadPool directly.
diskann-providers/src/utils/kmeans.rs	Updates k-means entrypoints to accept &RayonThreadPool directly.
diskann-providers/src/storage/index_storage.rs	Updates tests to pass a &RayonThreadPool into train_pq.
diskann-providers/src/model/pq/pq_construction.rs	Removes thread-pool generic type parameters and accepts &RayonThreadPool.
diskann-providers/src/model/graph/provider/async_/debug_provider.rs	Updates tests to create/pass &RayonThreadPool to PQ training.
diskann-providers/src/model/graph/provider/async_/caching/example.rs	Updates tests to create/pass &RayonThreadPool to PQ training.
diskann-providers/src/index/wrapped_async.rs	Updates tests to create/pass &RayonThreadPool to PQ training.
diskann-providers/src/index/diskann_async.rs	train_pq now takes &RayonThreadPool; updates all internal tests/callers.
diskann-disk/src/utils/partition.rs	Partitioning now takes &RayonThreadPool directly and threads it through helpers.
diskann-disk/src/storage/quant/pq/pq_generation.rs	PQ generation context/compressor updated to store/pass &RayonThreadPool.
diskann-disk/src/storage/quant/generator.rs	Quant data generator now takes &RayonThreadPool directly.
diskann-disk/src/build/builder/quantizer.rs	Creates a pool and passes &RayonThreadPool into PQ training during quantizer training.
diskann-disk/src/build/builder/core.rs	Updates partition call to match new partitioning signature.
diskann-disk/src/build/builder/build.rs	Updates quant data generation pipeline to pass &RayonThreadPool directly.
diskann-benchmark/src/backend/index/product.rs	Benchmark build path now creates a pool and passes &RayonThreadPool to PQ training.

Comments suppressed due to low confidence (1)

diskann-providers/src/utils/rayon_util.rs:15

• create_thread_pool is documented to treat num_threads == 0 as “default to logical CPUs”, but the implementation always calls ThreadPoolBuilder::num_threads(num_threads). This makes the behavior for 0 rely on Rayon internals and can fail (or at least be ambiguous), and there are callers in the workspace that pass 0. Consider handling num_threads == 0 explicitly (e.g., skip num_threads(...) / use available_parallelism, or clamp to >= 1) so the documented contract is enforced deterministically.

/// Creates a new thread pool with the specified number of threads.
/// If `num_threads` is 0, it defaults to the number of logical CPUs.
pub fn create_thread_pool(num_threads: usize) -> ANNResult<RayonThreadPool> {
    let pool = rayon::ThreadPoolBuilder::new()
        .num_threads(num_threads)
        .build()
        .map_err(|err| ANNError::log_thread_pool_error(err.to_string()))?;
    Ok(RayonThreadPool(pool))

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