feat(query): compile generic post-ASAP DAG bindings

[zzylol]

Summary

• compile every executable SummaryAgg leaf in a post-ASAP DAG, including SummaryMerge graphs
• bind each query node directly to its materialization fingerprint at physical compile time
• derive per-node metric identity from post-ASAP IR instead of serving-time BackendPlan candidate search
• lower unsupported post-ASAP operators to explicit exact-fallback nodes

Architecture

This completes the intended path: post-ASAP DAG -> PhysicalPlan materializations -> node-bound QueryPlan -> generic DAG executor. Query serving performs exact SID/sketch-store reads from the installed binding and never searches materialization candidates.

This PR is stacked on #477 and should be reviewed after it. It must not be merged independently.

Validation

• cargo test -p control_plane physical::compiler::tests (17 passed)
• cargo test -p control_plane query_plan (8 passed)
• cargo test -p data_plane physical_dag (1 passed)
• cargo check -p data_plane