Compute EXPECTED_BUCKETS_PER_KEY instead of hardcoding it to 1 #575

Problem

In SimpleEngine::execute_and_merge_store_queries (asap-query-engine/src/engines/simple_engine/mod.rs), the Sliding-window branch hardcodes:

const EXPECTED_BUCKETS_PER_KEY: usize = 1;

This is only used to phrase a warn! when the store returns a different bucket count per key — it doesn't gate merge behavior (all buckets are merged regardless, per #570). But the constant itself is wrong whenever a sliding-window query's requested range spans more than one window width, per #554.

Formula

expected_buckets_per_key = (Total Range - Window Size) / Window Slide + 1

• Total Range = the query's requested range_ms (timestamps.end_timestamp - timestamps.start_timestamp), available in create_store_query_plan.
• Window Size = aggregation_config_for_value.window_size_ms.
• Window Slide = aggregation_config_for_value.slide_interval_ms.

Both are available on the same aggregation_config_for_value already read in create_store_query_plan. When Total Range == Window Size (today's only supported case), this reduces to 1, matching current behavior.

Related

• fix(query-engine): merge all sliding-window buckets per key instead of taking first #570 (merge all sliding-window buckets per key instead of taking first)
• Sliding window execution: support multi-window merge/subtract in query engine #554 (sliding window execution: support multi-window merge/subtract in query engine) — this is the case where expected_buckets_per_key would actually exceed 1.