dalgo2bigquery v0.3.0

Adds a read-only DALgo source for one selected BigQuery project and dataset, exposing table schema, declared keys, view metadata, and paged physical table rows. The source uses metadata and tabledata GET requests without submitting query jobs. Existing approved SQL execution and load APIs remain available.

Rows preserve exact integers and decimal values, raw binary data, SQL NULL, and temporal values. Reads enforce pagination, resource, identity and metadata checks; unsupported schema configurations fail explicitly. Index introspection remains unsupported, and paged reads are not an immutable snapshot.

Validated by independent review, race tests and vet on Linux/macOS/Windows, and a live Chinook Album comparison: all 347 rows and column metadata matched the pinned SQLite source across four pages. Full live dataset parity is not claimed by that proof.