fix: detect unconsumed tokens after parse to catch unbalanced braces (#445) - #475

…445)

ANTLR's default error recovery silently absorbed certain malformed queries
(e.g. missing opening braces) without ever calling the syntaxError listener,
producing a structurally different but syntactically valid parse tree and
leaving trailing tokens unconsumed.

Fix by comparing the document tree's stop-token index against the last
non-EOF token after parsing; throw ParseError if any tokens were skipped.

Also fix two test queries that had a genuine extra `}` that was previously
silently ignored: entities-query in federation_tests and
later-fragments-do-not-override-earlier in fragments_tests.