b41f34c090
Adds an optional afterExecutionId field to SearchRequest. When combined with a non-null timeFrom, ClickHouseSearchIndex applies a strictly-after tuple predicate (start_time > ts OR (start_time = ts AND execution_id > id)) so same-millisecond exchanges can be consumed exactly once across ticks. When afterExecutionId is null, timeFrom keeps its existing >= semantics — no behaviour change for any current caller. Also adds the SearchRequest.withCursor(ts, id) wither. Threads the field through existing withInstanceIds / withEnvironment witheres. All existing positional call-sites (SearchController, ExchangeMatchEvaluator, ClickHouseSearchIndexIT, ClickHouseChunkPipelineIT) pass null for the new slot. Task 1.2 of docs/superpowers/plans/2026-04-22-per-exchange-exactly-once.md. The evaluator-side wiring that actually supplies the cursor is Task 1.5.