v0.1.0 of analytics_toolkit

A pure-Dart in-memory query engine for dashboard-style analytics over normalized record collections. Renderer-agnostic. Changelog excerpt: Initial release. analytics_toolkitis a pure-Dart in-memory query engine for dashboard-style analytics over normalized record collections. Hosts declare data sources, build typed queries with measures and group-bys, and read back typed results — no chart library, no UI toolkit, no Flutter dependency. The host streams SourceRecords in; the executor returns AnalyticsResultout. This release establishes the foundational API surface: - Schema and values— SourceDefand FieldDeffor decla[...]