feat: integrate stable partitions with FRI V1

[LuQQiu]

Stable partitions can retain existing B-tree segments while compaction continues writing FRI V1. This implements the mixed lifecycle using #8972's RowMapWriter and RowMapReader, without duplicating the codec or migrating V1 history.

• Publish prepared stable partitions and immutable _row_maps/<uuid>/row_map.lance references atomically through Operation::Rewrite, with paired reader/writer capability flags.
• Keep stored segment bitmaps as source provenance. Derive coverage from the union of a logical index's segments, probe every contributor, and give directly indexed destinations priority over translated entries.
• Compose V1 and V2 by fragment lineage. Translate B-tree pages on cold, cached, and streamed reads with bounded row-map block reads; route Python remap_row_addrs through the same Rust translator.
• Preserve mappings across append/delete and subsequent eager or deferred V1 compaction. Reject changed sources and unresolved repartitioning, allow disjoint partitions to rebase, and protect committed mapping files during cleanup. The prepared-commit API requires an explicit AllowUnindexed policy to accept incomplete source coverage.

Experimental scope: physical row addresses, one storage base, and B-tree query/maintenance integration. Other affected index types fall back to scanning. Automatic clustering, coordinated draining/pruning, and cloning mixed datasets remain outside this implementation. This is a draft; the formal format-change process is deferred until the design is agreed.

Stack: #8972 → this PR, with base branch lu/friv2. Replaces closed #8978. GitHub's native stack API rejects fork PRs, so the dependency is represented by the PR base branch.

Validation: 17 FRI tests and 6 table-format/transaction/flag tests passed; 2 targeted Python regression tests passed. Workspace cargo fmt --all and cargo clippy --all --tests --benches -- -D warnings, Python uv run make lint, JNI Clippy, and commit hooks passed. The Python extension was rebuilt with make build.