Correct the misleading deprecation note in utils/numeric.py

The blanket 'DEPRECATED: use unified_numerical instead' header was inaccurate: angle_diff and angle_diff_array are DEFINED in utils/numeric.py (not in unified_numerical) and are the canonical public phase-difference API, re-exported via tnfr.utils. Only the scalar wrappers (clamp, clamp01, ...) delegate to unified_numerical. Clarify the header so it no longer points developers to the wrong module for angle_diff. Docstring only; angle_diff resolves to the same object via tnfr.utils and tnfr.utils.numeric, delta-NFR tests pass.

Author: TNFR AI Agent

src/tnfr/utils/numeric.py

@@ -1,6 +1,11 @@
 """Numeric helper functions and compensated summation utilities.
 
-DEPRECATED: Use src/tnfr/mathematics/unified_numerical.py instead.
+The scalar wrappers here (``clamp``, ``clamp01``, ``within_range``,
+``kahan_sum_nd``, …) are thin compatibility shims that delegate to the canonical
+:mod:`tnfr.mathematics.unified_numerical`.  The phase-difference helpers
+``angle_diff`` and ``angle_diff_array`` are **defined here** (they are not part
+of ``unified_numerical``) and are re-exported as the canonical public API via
+:mod:`tnfr.utils` — prefer ``from tnfr.utils import angle_diff``.
 """
 
 from __future__ import annotations