Complete native global-index lifecycle and search planning

[JingsongLi]

Purpose

Complete the Rust core and binding support needed by PyPaimon’s existing index lifecycle and explicit search APIs. Java/Paimon semantics remain the reference; no new Python index families are introduced.

Changes

• Build BTree/Bitmap and all five Vindex families on deletion-vector tables. Build indexes over physical row IDs, omitting deletion metadata from build splits; query readers apply deletion vectors from their captured snapshot.
• Allow global index builds on row-tracked append tables even when data evolution or query-time global-index optimization is disabled. Validate structural options against the actual table and resolve source data paths from its configuration, not procedure overrides.
• Expose read-only index-drop preparation and its Python binding. build() returns unpublished metadata deletions; execute() retains snapshot conflict validation and dry-run behavior. Commit failures never remove index files.
• Expose captured vector/full-text search source metadata for explicit Scan → Plan → Read, including primary-key payloads, uncovered files and physical ranges. Reuse the existing snapshot, DataSplit v1 and IndexFileMeta encodings; no new persistent wire format.
• Add a thin Python positional-I/O bridge around the reusable Rust Vindex reader. Rust owns query validation, filtering, actual hit counts, batching and score conversion, including filtered IVF-PQ searches with fewer valid hits than K.
• Honor per-query Vindex reader options without leakage and align search widths with Java’s conflict checks and strict integer parsing. Align raw Vindex/Lumina metric defaults and reject mixed persisted vector formats consistently in single/batch execute and scan APIs.

The binding references the existing locked paimon-vindex-core and roaring packages; no third-party version changes are introduced.

Validation

• cargo test -p paimon --locked --features fulltext --lib index_: 583 passed, four existing ignored.
• cargo test -p paimon --locked --features fulltext --lib search_: 174 passed.
• Final --lib vector_: 357 passed; --lib vindex::reader::tests: 23 passed.
• cargo +1.98.0 clippy --locked --all-targets --workspace --features fulltext,vortex -- -D warnings: passed.
• cargo fmt --all --check and diff checks: passed.
• Rebuilt the final Python binding locally: explicit search/append regressions 107 passed; low-level reader/metric/live-NULL regressions 59 passed plus 55 subtests; direct vector/Blob binding tests 48 passed.
• Broader companion REST Native index suite: 816 passed.
• Independent core/Java, reader-I/O and Python plan-transport review: no remaining actionable P1/P2 findings.

Companion PyPaimon PR: apache/paimon#10598. Python CI continues building apache/paimon-rust main.

[leaves12138]

Reviewed against Java Paimon semantics, including global-index identity/range coverage, deletion-vector handling, snapshot pinning, vector/full-text scan metadata, and Vindex reader option/score behavior.

No blocking issues found. The targeted Rust tests passed:

• 19 global-index drop-builder tests
• 50 de-vector-read tests
• 23 Vindex reader tests

All PR checks are green. Approving.