fix(logical-optimizer): move whole-expression top-k partitions onto the heap input

[zzylol]

Stack: #574 → #620 → #618 → #621 → #627 → #625 → #628 → #632 → #634 → #616 → #617 → #622 → #624 → #629 → #630 → #631 → #633 → #635 → #636 → #637 → #638 → #640 → #641

Rebased onto #638. At the chain tip (#641) the full gate passes.

Fixes #639

Problem

For topk by(job)(k, sum by(service, job)(rate(x[5m]))), Stage 1 builds a whole-expression heap that reads the raw rate rows and absorbs the inner sum. That heap kept the outer top-k's Reduction, whose keys are indices into the inner aggregate's output. Read against the rate rows, by(job) became by(ts), so the result lost job. The legacy search, removed in #635, remapped these keys.

Changes

• pass1/logical_candidates.rs: whole_expression_input now also returns the outer partitions mapped onto the heap's input. A new helper, partitions_over, matches each key by column (column_ref). It returns None, so the heap is not offered, when a key is missing or ambiguous in the input or the keys are given by without. realize builds the SummaryAgg with these partitions.
• Un-ignored planner_weighted_topk_binds_at_either_deployment_phase. It now asserts (job, value) pairs at both phases: api: 0.3125, 0.375 and batch: 80, 100.
• Added the Pass 1 unit test whole_expression_topk_partitions_index_the_heap_input. Every heap in an absorbing candidate partitions by job in its child's schema. Without the fix, it fails with ["ts"].

Test plan

• cargo fmt --all -- --check: clean
• cargo clippy --workspace --all-targets -- -D warnings: clean
• cargo test --workspace: 1282 passed, 0 failed, 13 ignored
• Example 1 is unaffected: example1_document_is_valid_and_committed_fixture_is_current passes, and tools/dag-viewer/examples/planner-layering-example1.json is unchanged.

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