v2.8.1 — dated schema-error reframe + key-events name fix

Corrects stale GA4 conversion-rate metric names (sessionConversionRate → sessionKeyEventRate, per GA4's 2024-05-06 key-events rename) in the alias map, docstring, and skills. Rewrites schema-hallucination errors into a stable what/why/skill-pointer form that tells the model its training may be out of date and routes it to search_schema (live property) and search_skills (maintained mapping) instead of guessing.