redash-query-runner-framework-ported-as-r-dash-connector-base

Redash’s query_runner framework (BaseQueryRunner, BaseSQLQueryRunner, BaseHTTPQueryRunner) is the connector foundation for R-Dash. All 70 bundled Redash runners are carried dormant and activatable via config without rebuild. Only Snowflake is active in v1; others are hot-activatable by setting RDASH_ENABLED_QUERY_RUNNERS. The register(cls) pattern and JSON Schema configuration_schema() must be preserved when porting.