fix: preserve preconfigured logging

[schultzjack]

Summary

• track successful configure_logging() calls in the logging module
• skip interface default logging setup when logging was already configured
• add regression coverage for DataDesigner() preserving a prior debug logging config

Testing

• uv run --group dev pytest packages/data-designer-config/tests/test_logging.py packages/data-designer/tests/interface/test_data_designer.py -q
• make check-config check-interface
• make test-config test-interface

Closes #388

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[greptile-apps]

Greptile Summary

This PR fixes a bug where DataDesigner.__init__ would silently overwrite a caller's pre-configured logging setup (e.g. debug level) with the interface's default INFO config. The fix introduces a module-level _logging_configured flag in logging.py that is set after a successful configure_logging() call, and guards the default-logging call in _initialize_interface_runtime() behind an is_logging_configured() check.

• logging.py: adds _logging_configured = False, sets it to True at the end of configure_logging(), and exposes is_logging_configured().
• data_designer.py: wraps the default configure_logging() call in _initialize_interface_runtime() with if not is_logging_configured() so any prior configuration is preserved.
• Tests: updates test_initialize_interface_runtime_runs_once to reset _logging_configured via monkeypatch (keeping the mock assertion reliable), and adds two new tests — one unit test for the flag itself, and one end-to-end regression that verifies a DEBUG config survives DataDesigner() construction.

Confidence Score: 5/5

Safe to merge — the change is minimal, targeted, and fully covered by new and updated tests.

The fix is a one-flag, one-guard change with no impact on the happy path (logging not pre-configured) and correct behaviour on the new path (logging pre-configured). The existing test_initialize_interface_runtime_runs_once was correctly patched to reset the new flag so its mock assertion stays valid. The regression test exercises the real code path end-to-end and cleans up logger state in a finally block.

No files require special attention.

Important Files Changed

Filename	Overview
packages/data-designer-config/src/data_designer/logging.py	Adds module-level _logging_configured flag, sets it at the end of configure_logging(), and exposes is_logging_configured() predicate — straightforward and correct.
packages/data-designer/src/data_designer/interface/data_designer.py	Guards the default configure_logging() call in _initialize_interface_runtime() behind is_logging_configured() — clean one-line change with no unintended side effects.
packages/data-designer-config/tests/test_logging.py	Adds a focused test for the new _logging_configured flag using monkeypatch for proper isolation.
packages/data-designer/tests/interface/test_data_designer.py	Adds regression test for preconfigured-logging preservation and fixes the existing test_initialize_interface_runtime_runs_once by resetting _logging_configured — necessary to keep the mock assertion reliable.

Sequence Diagram

%%{init: {'theme': 'neutral'}}%%
sequenceDiagram
    participant User
    participant logging as data_designer.logging
    participant iface as _initialize_interface_runtime

    User->>logging: configure_logging(LoggingConfig.debug())
    logging->>logging: set handlers, levels
    logging->>logging: "_logging_configured = True"

    User->>iface: DataDesigner(...)
    iface->>iface: _interface_runtime_initialized? → False
    iface->>logging: is_logging_configured()
    logging-->>iface: True
    iface->>iface: skip configure_logging() ✓
    iface->>iface: resolve_seed_default_model_settings()
    iface->>iface: "_interface_runtime_initialized = True"
    iface-->>User: DataDesigner ready (DEBUG logging preserved)

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sequenceDiagram
    participant User
    participant logging as data_designer.logging
    participant iface as _initialize_interface_runtime

    User->>logging: configure_logging(LoggingConfig.debug())
    logging->>logging: set handlers, levels
    logging->>logging: "_logging_configured = True"

    User->>iface: DataDesigner(...)
    iface->>iface: _interface_runtime_initialized? → False
    iface->>logging: is_logging_configured()
    logging-->>iface: True
    iface->>iface: skip configure_logging() ✓
    iface->>iface: resolve_seed_default_model_settings()
    iface->>iface: "_interface_runtime_initialized = True"
    iface-->>User: DataDesigner ready (DEBUG logging preserved)

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[schultzjack]

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