Add algorithm and benchmark for filtered range search

[magdalendobson]

This PR adds an algorithm for filtered range search to the DiskANN repository. Details of the algorithm, along with the experiments supporting it, are at this Wiki page.

This PR:

1. Adds the new algorithm to diskann, along with integration tests.
2. Adds the new algorithm as an option in diskann-benchmark, along with an integration test.
3. Adds filtered range groundtruth files in test_data.

Some enhancements/fixes to range search along the way:

1. Added range groundtruth in test_data for yfcc.
2. Fixed a bug where range search was not always honoring the maximum number of returned results.
3. Added integration tests for range search making sure a set maximum number of results is actually respected.

[Copilot]

Pull request overview

This PR introduces filtered range search into the diskann search stack and wires it into diskann-benchmark, along with new groundtruth artifacts and integration tests. It also tightens unfiltered range-search behavior to better respect max_returned and adds regression tests to prevent future violations.

Changes:

• Added FilteredRange search type to diskann (new implementation + exports) and created dedicated integration tests/baselines.
• Extended diskann-benchmark / diskann-benchmark-core to accept a new "filtered-range" search phase and run end-to-end integration tests.
• Added new (LFS-backed) range-search groundtruth files and test inputs.

Reviewed changes

Copilot reviewed 22 out of 32 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
test_data/yfcc/groundtruth_rad_75000.rangeres	Adds YFCC range-search groundtruth pointer (LFS).
test_data/yfcc/groundtruth_rad_110000_filtered.rangeres	Adds YFCC filtered-range groundtruth pointer (LFS).
test_data/disk_index_search/groundtruth_rad_125000_filtered.rangeres	Adds filtered-range groundtruth pointer (LFS) for benchmark integration test data.
diskann/test/generated/graph/test/cases/range_search/max_results_respected_means_no_second_round.json	New baseline for range-search max_returned behavior.
diskann/test/generated/graph/test/cases/range_search/max_results_respected_and_second_round_triggered.json	New baseline for second-round triggering when max_returned allows it.
diskann/test/generated/graph/test/cases/filtered_range_search/two_round_search.json	New filtered-range baseline.
diskann/test/generated/graph/test/cases/filtered_range_search/max_results_respected_means_no_second_round.json	New filtered-range baseline.
diskann/test/generated/graph/test/cases/filtered_range_search/max_results_respected_and_second_round_triggered.json	New filtered-range baseline.
diskann/test/generated/graph/test/cases/filtered_range_search/inner_radius_filtering.json	New filtered-range baseline for inner radius behavior.
diskann/test/generated/graph/test/cases/filtered_range_search/divisible_by_four_filter_second_round_triggered.json	New filtered-range baseline for selective filter + second round.
diskann/test/generated/graph/test/cases/filtered_range_search/divisible_by_four_filter_no_second_round_from_max_results.json	New filtered-range baseline for selective filter + max_returned interaction.
diskann/test/generated/graph/test/cases/filtered_range_search/divisible_by_four_filter_no_second_round_from_l_search.json	New filtered-range baseline for selective filter + larger starting_l.
diskann/test/generated/graph/test/cases/filtered_range_search/basic_range_search.json	New filtered-range baseline for basic search.
diskann/src/graph/test/cases/range_search.rs	Exposes shared helpers/baseline struct and adds new max_returned regression tests.
diskann/src/graph/test/cases/mod.rs	Registers new filtered-range test module.
diskann/src/graph/test/cases/filtered_range_search.rs	Adds integration tests and baselines for filtered range search.
diskann/src/graph/search/range_search.rs	Ensures second round + frontier expansion honor max_returned.
diskann/src/graph/search/mod.rs	Adds filtered-range module and re-exports FilteredRange.
diskann/src/graph/search/inline_filter_search.rs	Makes internal return type/function pub(crate) for reuse by filtered-range search.
diskann/src/graph/search/filtered_range_search.rs	Implements the new FilteredRange search type and its internal second-round expansion.
diskann/src/graph/glue.rs	Adds PartialEq/Eq derives for Decision<T>.
diskann-benchmark/src/main.rs	Adds benchmark integration tests for range and filtered-range JSON examples.
diskann-benchmark/src/inputs/graph_index.rs	Adds "filtered-range" search phase schema + validation.
diskann-benchmark/src/index/search/range.rs	Generalizes range runner to support both range and filtered-range backends via parameter mapping.
diskann-benchmark/src/index/search/plugins.rs	Adds filtered-range plugin entry.
diskann-benchmark/src/index/result.rs	Adds RangeSearchResults::new_filtered constructor for filtered-range summaries.
diskann-benchmark/src/index/inmem/spherical.rs	Wires filtered-range plugin into spherical in-mem benchmark path.
diskann-benchmark/src/index/benchmarks.rs	Wires filtered-range plugin into benchmark registry + job runner.
diskann-benchmark/example/graph-index-filter-range.json	Adds example job config for "filtered-range".
diskann-benchmark-core/src/search/mod.rs	Documents filtered-range support.
diskann-benchmark-core/src/search/graph/mod.rs	Exposes new filtered_range module.
diskann-benchmark-core/src/search/graph/filtered_range.rs	Adds benchmark-core searcher + aggregation plumbing for filtered-range.

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