Fix: Variable overrides for dbt packages

[izeigerman]

I've realized that I missed another edge case.

[Copilot]

Pull Request Overview

This PR fixes an edge case in variable override handling for dbt packages by ensuring that SQLMesh config variable overrides are properly applied to all packages.

• Adds variable override application to ensure SQLMesh config variables take precedence over dbt project variables
• Introduces test coverage to verify variable overrides work correctly across all packages

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
tests/fixtures/dbt/sushi_test/config.py	Adds test configuration with variable overrides
tests/dbt/test_config.py	Adds test to verify variable overrides are applied to all packages
sqlmesh/dbt/project.py	Ensures variable overrides are applied to all packages after other variable resolution

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[Copilot]

The variable override logic is duplicated - it's already applied in all_project_variables on line 102. This second application is redundant since all_project_variables already includes the overrides and is applied to packages on lines 109 and 115.

Suggested change

	if variable_overrides:
	package.variables.update(variable_overrides)

[izeigerman]

Wrong! Below is the scenario the previous logic didn't handle:

For a variable with name package_var and the following setup:

1. --var 'package_var: overridden_from_cli'
2. In the project's dbt_project.yml:

vars:
  target_package:
    package_var: overridden_from_root_project

3. In the package's dbt_project.yml:

vars
  package_var: default_value

The old logic returned overridden_from_root_project instead of overridden_from_cli.