Add QueryBuilder with fluent API and composable filter expressions

Implements the QueryBuilder feature from the SDK redesign design doc:
- Fluent query builder (client.query.builder("table")) with 20 chainable methods
- Composable filter expression tree (models/filters.py) with &, |, ~ operators
- filter_in, filter_between, and where() for expression tree composition
- Automatic column name lowercasing and OData value formatting
- datetime/date/uuid.UUID auto-formatting in filter values

309 tests passing (126 new for QueryBuilder + filters).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: tpellissier

src/PowerPlatform/Dataverse/models/__init__.py

@@ -1,6 +1,19 @@
 # Copyright (c) Microsoft Corporation.
 # Licensed under the MIT license.
 
-"""Data models for Dataverse metadata types."""
+"""
+Data models and type definitions for the Dataverse SDK.
+
+Provides dataclasses and helpers for Dataverse entities:
+
+- :class:`~PowerPlatform.Dataverse.models.query_builder.QueryBuilder`: Fluent query builder.
+- :mod:`~PowerPlatform.Dataverse.models.filters`: Composable OData filter expressions.
+- :class:`~PowerPlatform.Dataverse.models.upsert.UpsertItem`: Upsert operation item.
+
+Import directly from the specific module, e.g.::
+
+    from PowerPlatform.Dataverse.models.query_builder import QueryBuilder
+    from PowerPlatform.Dataverse.models.filters import eq, gt
+"""
 
 __all__ = []