Query-time summary build reads unstored ingestion-time rows and still validates #738

Problem, by example

Take a DAG where the rows below a summary build only exist at ingestion time, nobody stores them, and the build itself runs at query time:

SummaryAgg(Kll)                 timing: QueryTime,     NotMaterialized
  └─ <rows node>                timing: IngestionTime  (fixed, e.g. by its own consumer), NotMaterialized
       └─ Scan(latency_ms)

Today: timing validation accepts this plan. The SummaryAgg.child edge rule in crates/types/src/ir/timing.rs (validate_asap) accepts ExecutionDataState::INGESTION_ROWS whatever the build's own timing. It only rejects a query-time value under an ingestion-time build:

match state_of(child) {
    ExecutionDataState::INGESTION_ROWS | ExecutionDataState::QUERY_ROWS => {}   // accepted at any timing
    ...
}
if timing == IngestionTime && avail.timing == QueryTime { return Err(QueryTimeValueUnderIngestionSummary { .. }) }

At query time, nothing holds those ingestion-time rows: they were not stored (NotMaterialized), and the query-time build cannot see the ingestion stream. The plan validates but cannot be executed.

Expected: the same rule a NonASAP consumer already follows (edge-rule table, last row). A query-time consumer reads either rows at its own timing, or a MatAtIngestion input's stored output. A query-time SummaryAgg over unstored ingestion-time rows is rejected with a clear error.

Cause

The SummaryAgg.child / PaneChain.child rule has no "stored or same timing" check for rows. The NonASAP rule has one.

Proposal

In validate_asap, refuse SummaryAgg / PaneChain at QueryTime whose child is INGESTION_ROWS from a node that is not MatAtIngestion. Add a new ExecutionDataStateError variant naming the edge, and add the row to the edge-rule table.

Rejecting this changes which plans validate. Before doing it, check:

• whether Stage 2 ever produces such an assignment; it should not, because its options keep a build and its rows on the same timing;
• which tests build such plans by hand.

Scope / acceptance

• A unit test with the DAG above: validation fails with the new error. The same DAG with the rows node MatAtIngestion validates.
• Examples 1–4 select the same plans at the same costs.

Status / related

Deferred by decision on 2026-10-16. Found in the #667 timing review and listed as row 14 of #737's nit table. Related: #730 (raw-data retention), #717 (Stage 2 materialization).