Replace failed rows diagnostics TODO print with a warning

[wunianze666-netizen]

Summary

• replace the TODO print(...) in SodaCloud.send_failed_rows_diagnostics() with a structured warning
• add a regression test that asserts the method does not write to stdout

Why

A bare print() in production code can leak implementation details into CLI output and make automation harder to reason about. Logging keeps the current placeholder behavior visible without polluting standard output.

Validation

• py -m uv run --package soda-tests pytest soda-tests/tests/unit/test_soda_cloud.py -k test_send_failed_rows_diagnostics_logs_warning_without_stdout -q (1 passed, 34 deselected)
• the remaining tests in that file reached 30 passed; five integration-backed cases require the optional soda_postgres package in the local environment
• git diff --check

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[CLAassistant]

All committers have signed the CLA.