Fix P3: stale test docstring and Rust private naming note

- Rewrite test_global_method_alias docstring to match its actual
  assertion (validates method="global" produces valid ATT)
- Add comment in Rust explaining that only exported #[pyfunction]
  names were renamed; private helpers retain *_joint* names

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: igerber

rust/src/trop.rs

@@ -1082,6 +1082,10 @@ pub fn bootstrap_trop_variance<'py>(
 
 // ============================================================================
 // Global method implementation
+//
+// Note: Only the #[pyfunction] exports were renamed (joint → global) to match
+// the Python public API. The private Rust helpers below retain their original
+// `*_joint*` names to keep the Rust-only rename scope minimal.
 // ============================================================================
 
 /// Compute global weights for global method estimation.

tests/test_trop.py

@@ -3275,7 +3275,7 @@ def test_global_rejects_staggered_adoption(self):
             trop.fit(df, 'outcome', 'treated', 'unit', 'time')
 
     def test_global_method_alias(self, simple_panel_data):
-        """method='global' works and produces same results as deprecated 'joint'."""
+        """method='global' runs and produces a valid positive ATT."""
         trop_est = TROP(
             method="global",
             lambda_time_grid=[0.0, 1.0],