add cdev group and pin gcovr, meson

Author: jeromekelleher

python/pyproject.toml

@@ -101,6 +101,13 @@ lint = [
     "prek==0.3.3",
 ]
 
+# Used to specify versions in CI. For local dev use
+# you can use e.g. ``uv tool install meson`` to install.
+cdev = [
+    "gcovr",
+    "meson",
+]
+
 dev = [
     {include-group = "docs"},
     {include-group = "lint"},