Fix F001 & F002: Update error message assertions for coglet-alpha compatibility
Updated test assertions to accept coglet-alpha's different error message formats:
- F001 (test_build_without_predictor): Accept JSON formatted errors without requiring 'Failed to get type signature'
- F002 (test_build_invalid_schema): Accept AssertionError format 'default=1 conflicts with ge=2' alongside original format
Both tests now maintain backward compatibility with original cog while supporting coglet-alpha