Build a baseline Decision Tree classifier

Train a baseline DecisionTreeClassifier using standard library tools with default parameters. Report accuracy, precision, recall, and F1-score on both train and validation splits. Add a short note on whether the default tree shows signs of overfitting.

No file or test is named in the issue. Start by locating the repository's notebook or classifier entry point and confirming how the train and validation splits are represented. Train the default decision tree, report accuracy, precision, recall, and F1 on both splits, and document whether the results indicate overfitting.

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