Fix path-pattern mixing logic in registerRelationship

[Copilot]

The validation logic in registerRelationship treated all path relationship identifiers as definitions, reporting DuplicateDefinition even when a pattern definition like [r | a, b] was followed by consistent path usage (a)-[r]->(b). This made mixed notation impossible.

Changes

• Gram/Validate.hs: Modified registerRelationship to check SymbolType when an identifier exists:

  • TypeRelationship (from another path) → DuplicateDefinition
  • TypePattern (from bracket notation) → verify arity consistency, allow if arity matches 2

• SemanticsSpec.hs: Fixed arity mismatch test to define all referenced elements and check for InconsistentDefinition among errors

• Test.hs: Added missing SemanticsSpec import

Example

-- Now validates correctly:
validateSource "[r | a, b], (a)-[r]->(b)"  -- Right () (consistent)
validateSource "(a)-[r]->(b), (c)-[r]->(d)"  -- Left [DuplicateDefinition r]
validateSource "[r | a, b, c], (a)-[r]->(b), (c)"  -- Left [InconsistentDefinition r ...]

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