feat(ingest/tableau): log Initial SQL + lineage and warn when none parses

[treff7es]

Summary

Adds diagnostics to the Tableau Initial SQL lineage path so a run that produces no Initial-SQL lineage can be debugged directly from the ingestion output, and so the most common silent-failure mode becomes visible.

Motivation: investigating a case where a data source's Initial SQL was captured as the initialSql custom property but produced no upstream lineage, with nothing in the report explaining why. The cause turned out to be Initial SQL whose line breaks were lost: a leading -- line comment with no terminating newline collapses the entire script into a single comment, so split_statements yields zero statements. This is not a parse failure, so it incremented no counter and emitted no warning — completely silent.

Changes

• Per-data-source DEBUG log of the dataset URN, the raw Initial SQL (via repr(), so newline boundaries are visible), and the upstream URNs it produced. Run ingestion with --debug to see exactly what the connector received and what lineage it derived.
• Structured report warning + counter (num_initial_sql_connections_without_statements) when a non-empty Initial SQL splits into zero statements. The warning context reports has_newline / has_line_comment, which immediately tells you whether the SQL arrived with its line breaks intact.
• New counter num_initial_sql_statements_parsed for visibility into how many statements were extracted across all connections.

No change to lineage emission behavior.

Testing

• New unit test test_get_initial_sql_lineage_flattened_comment_warns_and_counts covers the zero-statements case (raw SQL still captured, no upstreams, counter incremented, not counted as a parse failure).
• Strengthened the existing multi-statement test to assert num_initial_sql_statements_parsed and that the zero-statements counter stays 0.
• metadata-ingestion:lintFix and targeted mypy pass on the changed files; full tests/unit/tableau/test_tableau_initial_sql.py suite passes (47 tests).

Checklist

• PR conforms to the Contributing Guideline (PR Title Format)
• Tests added
• Docs (none required — observability only)
• Breaking changes (none)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ All tests successful. No failed tests found.

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[datahub-connector-tests]

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