Feat(dbt): Add support for adapter.expand_target_column_types

[vchan]

No description provided.

[Copilot]

Pull Request Overview

This PR adds support for the adapter.expand_target_column_types dbt method in SQLMesh. The feature allows expanding column types in a target table to match those of a source table when safe to do so (e.g., increasing varchar length).

Key changes:

• Implements the expand_target_column_types method in the adapter interface
• Adds logic to compare column types and generate appropriate ALTER TABLE statements
• Updates documentation to reflect the newly supported method

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
sqlmesh/dbt/adapter.py	Adds abstract method definition and concrete implementation for expanding column types
tests/dbt/test_adapter.py	Adds comprehensive test coverage for the new expand_target_column_types functionality
docs/integrations/dbt.md	Removes expand_target_column_types from unsupported methods list

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