Sprint 239 Plan: Native Semantic Reason Enrichment

Goal

Increase semantic signal quality in native task decomposition without relying on fallback expansion.

Step 2238: Add optional native reason enrichment before fallback evaluation.
Step 2239: Derive semantic tags from injected semantic requirement kinds.
Step 2240: Attach enriched reason tags to native task reasons deterministically.
Step 2241: Emit native reason enrichment telemetry in pipeline summary.
Step 2242: Add Sprint239IntegrationSummary.h and execution tracker.