Fix CI failures: validate_file return type, missing SPDX headers, test arg typo

[Copilot]

Three independent bugs were causing CI to fail across lint and all test matrix entries.

Changes

• validator.py — validate_file() return value (root cause of 24 test failures): Method signature declared -> tuple[list[...], int, ast.AST | None] but the body unpacked _validate_file_with_metrics() and returned only issues. Every caller (tests + validate_files()) destructured the result as issues, _, _ = validator.validate_file(...), producing ValueError: not enough values to unpack.

  # before
  issues, _, _ = self._validate_file_with_metrics(file_path)
  return issues
  
  # after
  return self._validate_file_with_metrics(file_path)

• CHANGELOG.md, cliff.toml — missing SPDX headers: reuse lint failed because these two files had no copyright/license information. Added standard SPDX headers matching the rest of the repo.

• test_ast_parser.py — spurious argument in one test: test_annotated_assignment_attribute_target called parser.parse_file(file_path, "test.module") but parse_file only accepts file_path. Removed the extra argument.

Original prompt

Please investigate why the tests are failing in CI and get them passing again :)

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[Copilot]

Pull request overview

This PR fixes CI failures across tests and reuse lint by aligning APIs with their declared signatures and ensuring SPDX/REUSE compliance for non-code files.

Changes:

• Fix LateImportValidator.validate_file() to return the full metrics tuple as declared (issues, lateimport count, AST).
• Add missing SPDX headers to CHANGELOG.md and cliff.toml to satisfy reuse lint.
• Fix a unit test calling ASTParser.parse_file() with an invalid extra argument.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
tests/test_ast_parser.py	Removes an invalid extra argument to parse_file() so the test matches the parser API.
src/exportify/validator/validator.py	Makes validate_file() actually return the declared 3-tuple to prevent unpacking errors in callers/tests.
cliff.toml	Adds SPDX header for REUSE compliance.
CHANGELOG.md	Adds SPDX header (HTML comment style) for REUSE compliance.

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[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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