Rename classifiers/ package to models/

Aligns module naming with the upcoming classification_neural lab,
which will use the same models/ package convention.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

models/manual.py

@@ -0,0 +1,12 @@
+import numpy as np
+
+
+class ManualClassifier:
+    def fit(self, X, y):
+        return self
+
+    def predict(self, X):
+        return np.array([self.predict_one(msg) for msg in X])
+
+    def predict_one(self, message):
+        return "ham"