GH-4181: Validate TRIPLE argument ranges

[linhongyu510]

GitHub issue resolved #4181

Fixes #4181.

Pull request Description:

TRIPLE() now enforces the SPARQL 1.2 RDF triple argument ranges regardless of ARQ strict mode:

• subjects must be IRIs or blank nodes;
• predicates must be IRIs;
• objects must be IRIs, blank nodes, literals, or triple terms.

The implementation also fixes the invalid-subject error message to report the subject argument rather than the predicate. Regression tests cover literal and triple-term subjects plus a non-RDF extension node in object position. Existing non-strict tests were updated because SPARQL 1.2 requires these invalid tuples to raise an evaluation error unconditionally.

Verification:

mvn -pl jena-arq -am \
  -Dtest=TestExprTripleTerms,TestExpressions \
  -Dsurefire.failIfNoSpecifiedTests=false test

Tests run: 301, Failures: 0, Errors: 0, Skipped: 0
BUILD SUCCESS

The same commit was also exercised by the full repository suite:

Tests run: 19717, Failures: 0, Errors: 0, Skipped: 12

AI Assistance Disclosure:

AI assisted with implementation review and test planning. The author reviewed the diff and ran the verification commands above.

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• Tests are included.
• Documentation change and updates are provided for the Apache Jena website (not applicable; this aligns existing behavior with the SPARQL 1.2 specification and changes no Jena documentation surface).
• Commits have been squashed to remove intermediate development commit messages.
• Key commit messages start with the issue number (GH-xxxx)

By submitting this pull request, I acknowledge that I am making a contribution to the Apache Software Foundation under the terms and conditions of the Contributor's Agreement.

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See the Apache Jena "Contributing" guide.