Add zoned layout scan plan

[joseph-isaacs]

Summary

• add a ZonedPlan physical node with a transparent data child and auxiliary zones child
• construct it from both current vortex.zoned layouts and legacy vortex.stats layouts
• recursively optimize both child plans
• expose the node through the public plan API and new_plan dispatch
• add plan-tree snapshots for current and legacy zoned layouts

Stack

This draft is stacked on #9166 and targets vortex-plan-optimizer.

Scope

This PR represents the physical zoned layout without inventing execution semantics that the current plan IR cannot express. Zone-map pruning still needs a query-aware predicate/pruning plan and will be handled with plan execution in a later change.

Checks

• cargo test -p vortex-layout — 211 passed
• cargo clippy --all-targets --all-features
• cargo +nightly fmt --all -- --check
• git diff --check