Update changelog entry to reflect platlib support

The earlier draft only mentioned {py_purelib} staging; the actual
routing handles both {py_purelib} and {py_platlib}, which is what
real scientific-Python projects (pandas, numpy, scipy — all
pure: false) rely on. Also mention the canonical-name comparison
and the pure-Python case.

Author: fangchenli

CHANGELOG.rst

@@ -15,12 +15,16 @@ Unreleased
 ==========
 
 - Route files staged under ``{py_purelib}/<name>-<version>.dist-info/...``
-  into the wheel's ``.dist-info/`` directory at pack time. This is the
-  recommended mechanism for placing PEP 770 SBOMs and other dist-info-bound
-  metadata files in the wheel, removing the need for post-build wheel
-  surgery. Works with both static ``install_data()`` and dynamic
-  ``custom_target(install: true)``; requires no new meson API. The collision
-  check surfaces overlaps between files routed here and PEP 639
+  or ``{py_platlib}/<name>-<version>.dist-info/...`` into the wheel's
+  ``.dist-info/`` directory at pack time. This is the recommended mechanism
+  for placing PEP 770 SBOMs and other dist-info-bound metadata files in the
+  wheel, removing the need for post-build wheel surgery. Works with both
+  static ``install_data()`` and dynamic ``custom_target(install: true)``,
+  and with ``pure: false`` projects (which stage under ``{py_platlib}``)
+  as well as pure-Python packages. Requires no new meson API. The distinfo
+  directory name is compared canonically, so hyphens vs. underscores in the
+  user's ``meson.project_name()`` don't break routing. The existing
+  collision check surfaces overlaps between files routed here and PEP 639
   ``license-files`` written by the metadata layer. Routing is enforced for
   non-editable wheels; editable wheels do not include dist-info-bound files
   (a known limitation).