feat: add IVF-SQ L2 distance range search

[JunRuiLee]

Summary

Part of #97. Adds IVF-SQ L2 distance range search on top of current main, including the already-merged IVF-RQ support from #104.

• Support single and batch queries, each with or without a serialized Roaring allow-list, through both the unified and direct SQ readers.
• Reuse DistanceBand, VectorRangeSearchParams, RangeSearchResult, and the generic Collector scan seam. Membership is decided by the same blocked SQ-estimated squared-L2 values used by the SQ scanner, not original-vector distances or a capped top-K fallback.
• Preserve the existing top-K behavior, other metrics, bindings, and on-disk format. Existing RQ range support remains enabled.
• Document quantization-induced membership errors, half-open bounds, statistics, and the supported-family matrix.

Performance

• Retain blocked SIMD evaluation and finite-upper-cut early abandonment.
• Read each unique probed list once per batch, reuse the existing partition cache, and stream oversized lists in bounded chunks.
• Reuse scan scratch and query-owned collectors; large single queries merge once per list rather than once per row.
• Build compact, query-local filter masks once per list/chunk and share them across queries. Masks are not retained in the partition cache; fully excluded lists/chunks skip distance evaluation.

Coverage

• SQ-estimate oracle across all four entry points and multiple probe widths.
• Exact boundary inclusion/exclusion, unbounded and empty bands, no result cap, and a concrete distinction from original-vector membership.
• SIMD blocks/tails, query permutation and parallel scans, cache reuse, query-local filtering, partial-probe deduplication, and bounded multi-range reads.
• Oversized-list single/batch/filter paths, invalid queries and metrics, non-finite estimates, payload errors, and fallible streaming.
• A lookup-count regression test proves that three queries over 1,024 rows perform 1,024 filter lookups instead of 3,072.

Validation

Executed locally after rebasing onto c2d9436:

• cargo fmt --all -- --check
• cargo clippy --all-targets --workspace -- -D warnings
• cargo test -p paimon-vindex-core --lib: 553 passed, 1 existing ignored test.
• cargo test -p paimon-vindex-core --test range_search: 52 passed, including the existing Flat and RQ cases.
• cargo test -p paimon-vindex-core --release --test range_search: 52 passed.
• cargo test -p paimon-vindex-core --test storage_format_fixtures: 2 passed, 1 existing ignored fixture printer.

The exact CI Clippy invocation also supplies -A clippy::chunks-exact-to-as-chunks, which local Rust 1.95.0 does not recognize. The workspace Clippy command above passes without that lint allowance.

Linux/x86_64 and full cross-language CI remain for the repository workflows. There is no storage migration or binding change; reverting this additive PR does not require rewriting index files.

Known review follow-up

Independent review found no blocking issues. One non-blocking P2 hardening follow-up remains: SQ range coarse-probe selection uses the existing unchecked centroid ranking, so a non-finite centroid or an overflowed coarse squared distance in an unselected list can escape validation. This is a source-traced corruption/extreme-value case, not a newly reproduced ordinary-input failure. A follow-up should add SQ-range-only checked probe validation and tests for unselected NaN/overflow cases; existing top-K and RQ behavior remain unchanged here.

[jerry-024]

+1