Improve record failure logging for max_tokens-truncated parse/recipe failures

[eric-tramel]

Summary

When a record fails because the model response was truncated at max_tokens and the response recipe/parser then fails, the record-failure log is too generic. Users see a dropped-record warning and a parse/recipe failure, but not the actionable cause that the model likely stopped due to token budget exhaustion.

Current paths

• packages/data-designer-engine/src/data_designer/engine/dataset_builders/column_wise_builder.py:487
_worker_error_callback() only logs a generic dropped-record warning.
• packages/data-designer-engine/src/data_designer/engine/models/facade.py:323
• packages/data-designer-engine/src/data_designer/engine/models/facade.py:421
  Parse/recipe failures are wrapped as GenerationValidationFailureError after retries/restarts.
• packages/data-designer-engine/src/data_designer/engine/models/errors.py:216
  The validation failure text has a generic max_tokens hint, but it does not specifically call out truncation-driven parse failures at the record level.
• packages/data-designer-engine/src/data_designer/engine/models/clients/parsing.py:35
  Raw provider responses are already preserved in ChatCompletionResponse.raw, so the finish/stop reason may be recoverable from response metadata.

Requested change

If the completion stop reason indicates token-limit truncation (finish_reason == "length" or equivalent provider-specific stop_reason) and the failure is a parse/recipe failure, emit a more specific error/log message.

The message should say the response appears to have been cut off by max_tokens, that this caused the parse/recipe failure, and that the user should increase inference_parameters.max_tokens in the model config.

Acceptance criteria

• Record-failure logging explicitly mentions max_tokens truncation when both conditions are true:
  1. the stop reason indicates length/max-tokens termination
  2. the failure is parse/recipe-related
• The message recommends increasing max_tokens in the model config.
• Generic parse-failure messaging remains unchanged when truncation is not indicated.
• Tests cover the targeted logging/error text for this path.