Guard Claude converge skill against unsupported argument hints

[Copilot]

The Claude integration should not suggest that /speckit-converge accepts a feature-name argument. converge relies on existing feature context, so advertising an argument here is misleading.

• Regression guard

  • Added a focused Claude integration test to assert that converge is not present in ARGUMENT_HINTS.
  • This locks in the current behavior without changing production logic.

• Scope

  • No runtime behavior changes.
  • No broader integration or template updates beyond this review-comment fix.

def test_converge_has_no_argument_hint(self):
    assert "converge" not in ARGUMENT_HINTS