v0.2.7: canvas spillover fix, query-input echoes, error contract

canvas spillover fix, query-input echoes, error contract

Fixes DataCanvas spillover for EIA's {col}-units columns, echoes the applied query inputs back to callers, and declares the system-catalog rejection in the error contract.

Added:

• eia_query_route echoes appliedStart, appliedEnd, appliedFrequency, and appliedColumns via enrichment (populated only when provided; appliedColumns also renders in the content[] trailer) (#23)
• eia_dataframe_query echoes the executed SQL as a required executedSql output field and via enrichment (#23)
• eia_dataframe_query errors[] declares system_catalog_access (ValidationError) for the framework denySystemCatalogs rejection, so agents routing on data.reason self-correct toward df_ tables (#21)

Fixed:

• DataCanvas spillover for EIA's {col}-units companion columns: the hyphen failed the canvas identifier gate, so registration returned canvas_id: null and silently degraded to the inline preview for nearly every data query. Column identifiers are sanitized before registration ({col}-units → {col}_units); the staged table and eia_dataframe_describe report the sanitized names, while inline rows keep the hyphenated keys (#25)

165 tests pass; bun run devcheck clean.