feat(framework): Require license file in fab_format_version=1

[mohammadnaseri]

This PR adds an additional check to fab_format_version = 1 validation by requiring apps to declare a root-level license file in [project].license.file and ensuring that the declared file is actually included in the final FAB.

[Copilot]

Pull request overview

This PR tightens FAB format v1 validation by requiring apps to declare a root-level license file via [project].license.file and by verifying that the declared license file is actually present in the filtered FAB contents during build.

Changes:

• Add v1 validation for [project].license.file (must be LICENSE or LICENSE.md) and reject inline license text.
• Add v1 build-time contents validation to ensure the declared license file is included in the final FAB.
• Extend unit tests to cover the new v1 license requirements and FAB build behavior.

Reviewed changes

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

File	Description
framework/py/flwr/supercore/fab_format_version.py	Implements v1 license declaration parsing/validation and checks declared license file is included in filtered FAB paths.
framework/py/flwr/supercore/fab_format_version_test.py	Updates existing v1 tests for the new requirement and adds new unit tests for license validation rules.
framework/py/flwr/cli/build_test.py	Updates v1 build tests to include a license file and adds new build tests to assert missing/excluded license behavior.

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