fill_prof_email: cleaner hardware/platform wording (no 'OpenMM OpenMM')

Template said 'Hardware: ... (OpenMM {platform_hint} backend)' which
produced 'OpenMM CPU (OpenMM 8.5.1, no Metal in build) backend' when
the user passed --platform with 'OpenMM' in it. Splitting into two
clean lines: 'Hardware: ...' and 'OpenMM platform: ...'. Test updated
to match. 10/10 still pass.

Author: Rockman6

scripts/fill_prof_email.py

@@ -47,7 +47,8 @@
 
 == What ran ==
 
-- Hardware: {hardware_hint} (OpenMM {platform_hint} backend)
+- Hardware: {hardware_hint}
+- OpenMM platform: {platform_hint}
 - Force field: OpenFF Sage 2.1.0 (small molecules) + AM1-BCC partial
   charges + TIP3P water — no learned surrogate at any layer
 - MD: openmmtools.alchemy + GHMC integrator (Metropolised Langevin),

tests/fep/test_fill_prof_email_smoke.py

@@ -246,7 +246,7 @@ def test_hydration_hardware_override_lands_in_body():
     assert "Henry's MacBook Pro M-series, 16 GB RAM" in out, (
         "hydration body must use --hardware override; got:\n"
         f"{out[:800]}")
-    assert "OpenMM CPU (Reference/CPU only; no Metal) backend" in out, (
+    assert "OpenMM platform: CPU (Reference/CPU only; no Metal)" in out, (
         "hydration body must use --platform override; got:\n"
         f"{out[:800]}")
     # The old M5 Max hardcoding must be gone for the hydration path.