[Feature][PPL] Apply Calcite post-processing to pushed aggregation snapshots

[penghuo]

Parent: #5765

Goal

Return current results when an eligible pushed aggregation has Calcite operators above the aggregation leaf.

Scope

• Detect the eligible pushed aggregation leaf from the optimized physical plan.
• Store aggregation-boundary rows with REPLACE semantics.
• Replace the aggregation leaf with a StateStoreScan for current-result evaluation.
• Compile the residual Calcite plan once and reuse it for subsequent POST timeout and GET reads.
• Do not reparse, reoptimize, or restart the primary query during polling.

Acceptance criteria

• Queries such as pushed stats followed by partial-safe eval or fields can return meaningful current results.
• Every read evaluates the cached residual plan against one coherent StateStore view.
• The primary query still executes once and remains the authoritative final path.
• Final output exactly matches synchronous Calcite PPL output.
• Ambiguous or unsupported physical shapes fail classification safely and do not publish semantically invalid rows.
• Concurrent StateStore replacement, preview evaluation, cancellation, and close are covered by tests.