Move execution timing out of the logical DAG, then rename PostAsapDag — after #511 #520

Goal

Under #509, logical planning decides what to compute. Physical planning decides materialization, i.e. when: ingestion time or query time. On main, ExecutionTiming is still part of logical node payloads and of node identity. Move it to the physical side, then rename the post-ASAP DAG family to #509's names.

Blocked on

Implementation of #511 (unified operator graph: OperatorNode with common metadata, no KeepPreAsap wrappers). Do not start before #511 is implemented.
#511 places timing as common node metadata: OperatorNode { timing: Option<ExecutionTiming> }, left None on logical candidates and required on executable physical candidates (operator-sharing.md ~:65, :349, :358, :507-520). Settle with #511 whether timing is that field or a physical-side per-node map.

Current state (main @107ab28d)

• Defined: ExecutionTiming / ExecutionDataState (types/src/post_asap/execution_data_state.rs:60-116). There are timing fields on BinaryOp, ValueOperation and SummaryMerge (expr.rs:140,151,263). It is serialized in PostAsapDagNode.output_state and in edge data_state (post_asap_dag.rs:93-114; POST_ASAP_DAG_WIRE_VERSION = 6).
• Stamped in Pass 1: about 10 QueryTime and 3 IngestionTime sites in replacement.rs. exact_composition.rs:199-205 maps placement to timing, which creates separate ValueOperationAtQueryTime / AtIngestionTime candidates.
• Read in logical validation and CSE: validate_execution_data_states (execution_data_state.rs:288-590) uses timing to give nodes their meaning. For example, an ingestion-time BinaryOp must be identity-aligned single-column arithmetic, and checked division is query-time only. cse.rs includes timing in node identity.
• Overridden after lifecycle selection: execution_timed_dag() (summary_maintenance_lifecycle.rs:236-300) re-stamps every node through PostAsapDag::with_execution_phases.
• Consumed by the physical planner: the cut frontier (candidates.rs:96-123) and lowering (mod.rs:466,649; precompute.rs:228; promql_rows.rs:277).

Latent bug: under an Ephemeral lifecycle, a BinaryOp that Pass 1 validated as ingestion-time arithmetic is re-stamped QueryTime, so it is lowered differently from how it was validated.

Proposed (recommendations; revisit against #511)

PR1: move timing out (wire 6→7)

1. Remove timing from the logical payloads. Express the ingestion-time BinaryOp's meaning on the operator itself, e.g. an identity_aligned flag on BinaryOperator, and use it in both validation and lowering. This also fixes the latent bug; add a test for it.
2. Keep the maintenance and read variants only as different graph shapes, with no timing label.
3. Have execution_timed_dag return the phase map it already builds (BTreeMap<NodeId, ExecutionTiming>). compile, frontier_from_timing and precompute take that map. Delete with_execution_phases, and move its query-feeds-ingestion check into frontier_from_timing.
4. Drop timing from CSE identity, so sharing ignores placement.
5. DAG node and edge states keep only DataPrimitive.

Estimate: about 20 src and 15 test files, roughly 600-900 lines.

PR2: pure rename (no wire bump; serde does not write type names, and the dag-viewer kind contract checks only SummaryExpr/QueryExpr kinds)

About 41 files. This follows #514, which renamed PlanSpace → CandidateLogicalASAPDAGs and PhysicalCandidate → PhysicalASAPDAG.

Open questions

• Timing: a per-node physical map, or docs: define unified operators and SQL/PromQL scalar boundaries #511's Option field set by physical planning?
• Keep the phase map derivable, or store it on QueryLifecyclePlan?