settings: box the loose keycam row under a Mouse heading

Guides, Startup and Units are sections and already draw as boxes;
drag_sensitivity sat above them as a bare row. Same `group` mechanism as
the Node Graph tab, so the JSON key is unchanged.

Co-Authored-By: Claude Fable 5.1 <[email protected]>

 python3.13libs/hc/hcschema.py | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/python3.13libs/hc/hcschema.py b/python3.13libs/hc/hcschema.py
index b7a48b1..045d1ea 100644
--- a/python3.13libs/hc/hcschema.py
+++ b/python3.13libs/hc/hcschema.py
@@ -117,7 +117,12 @@ SCHEMA = {
             "delta_z":  Setting("float", 1.0, label="Zoom Step"),
             "delta_ow": Setting("float", 1.0, label="Ortho Width Step"),
         },
-        "drag_sensitivity": Setting("slider", 0.25, range=(0.0, 1.0)),
+        # Guides, Startup and Units are sections and box themselves; this
+        # one is a loose value, so it gets a heading like the node graph rows.
+        "drag_sensitivity": Setting(
+            "slider", 0.25, range=(0.0, 1.0), group="Mouse",
+            help="How far a mouse drag tumbles the camera, from smooth to twitchy.",
+        ),
     },
     "node_graph": {
         # Groups are panel headings only; the keys stay flat in the file.