[JingsongLi]

Purpose

Move the remaining distributed row-ID range lookup and deletion grouping behind execution dispatch, and finish placing the corresponding Python bucket execution implementations under execution/python. Public PyPaimon and Ray API signatures remain unchanged.

Changes

• Give captured row-ID plans matching Python and Native route, route_by_bucket and read-only select execution contracts.
• Delegate Native routing to Core's existing RowIdPlan with Arrow inputs. Worker serialization drops only the SDK handle and reconstructs the same captured typed plan; it does not replan, reselect a backend or replay execution errors in Python.
• Remove repeated NumPy range lookup from Ray read/update/delete callbacks and replace pickle/base64 deletion keys with typed per-partition/bucket routing IDs. Keep Ray scheduling and existing worker authorization, liveness checks and commit messages.
• Keep complete file groups, deletion vectors, authorization, paths and snapshot metadata during read selection.
• Match Core's normal-anchor ownership when a Blob/vector file spans multiple groups: attach it to overlapping groups without joining anchors or filling row-ID gaps. Preserve planning work and LIMIT statistics while copying and refreshing the selected plan's final output counters, including after pickle.
• Move Python-only bucket hashing, HASH index restoration and stateful assignment into execution/python. Keep shared limits, validation and read-view configuration outside execution. Update internal imports and packaging without compatibility reexports or SDK version probes.

Verification

• 5 real Ray cases passed: cross-file reads and updates, updates with deletion vectors, partial-column evolution files and Blob reads.
• 295 current-SDK integration tests passed, exercising routing, plan serialization, captured-snapshot updates/deletes, selected reads and existing distributed bucket execution. No Native extension was installed or rebuilt for these Python tests.
• Independent Python row-ID regression collection: 87 passed, 4 skipped without an installed SDK; those Native paths passed in the joint collection. Bucket regressions: 158 passed (collections overlap).
• Actual wheel-content validation passed. Changed-file Flake8 and diff checks passed.

Depends on apache/paimon-rust#1209. This PR will remain draft until the companion Rust API reaches main. Native CI continues to build Rust main; no CI pin or compatibility fallback is added.

[leaves12138]

LGTM