Rich logging still auto-enabled in sagemaker.core

**PySDK Version**
PySDK V3

**Describe the bug**

[sagemaker/core/__init__.py:4](https://github.com/aws/sagemaker-python-sdk/blob/master/sagemaker-core/src/sagemaker/core/__init__.py#L4) unconditionally calls enable_textual_rich_console_and_traceback() at import time, which installs Rich tracebacks (rich.traceback.install) and replaces the root logger with RichHandler the moment sagemaker is imported.

[aws/sagemaker-core#325](https://github.com/aws/sagemaker-core/pull/325) (merged Aug 2025) fixed this in the standalone sagemaker-core package by making Rich opt-in, but that change was never applied to the bundled copy in sagemaker-python-sdk.

To reproduce
```

import sagemaker

# Rich tracebacks are now globally installed
# Rich logging handler is now the root handler
# Any SageMaker job output (processing, training) renders with Rich formatting

from sagemaker.core.helper.session_helper import Session
from sagemaker.core.processing import FrameworkProcessor

sess = Session()

processor = FrameworkProcessor(
image_uri="",
role="",
instance_type="ml.m5.xlarge",
instance_count=1,
)

processor.run(code="script.py", source_dir="source_dir", wait=True)
# Output is non-scrollable Rich-formatted text in Jupyter
```

**Expected behavior**

Rich logging should be opt-in (as intended by [sagemaker-core#325](https://github.com/aws/sagemaker-core/pull/325)), not automatically enabled on import. Job outputs in Jupyter notebooks should be scrollable plain text by default.

**Screenshots or logs**

**System information**
SageMaker Python SDK version: 3.4.1 (sagemaker-core 2.4.1)
Python version: 3.11

Commencez par sagemaker-core/src/sagemaker/core/__init__.py:4 et comparez sa configuration de Rich au moment de l’importation avec le comportement opt-in décrit dans aws/sagemaker-core#325. Vérifiez que l’importation de sagemaker n’installe plus les tracebacks Rich et ne remplace pas le logger racine, et que la sortie signalée des jobs Jupyter reste par défaut en texte brut et défilable.

Rédigé par le modèle d'indexation à partir du texte de l'issue.