better cam ref UI and clear keyframe ops

1.0.4:

- UI: Better cam ref exposition in Toolbox panel
  - Access to opacity
  - merge activation bool with source type icon
- feat: Added a clear active frame operator (`gp.clear_active_frame` to add manually in keymaps)

OP_helpers.py

@@ -449,6 +449,38 @@ class GPTB_OT_overlay_presets(bpy.types.Operator):
         
         return {'FINISHED'}
 
+class GPTB_OT_clear_active_frame(bpy.types.Operator):
+    bl_idname = "gp.clear_active_frame"
+    bl_label = "Clear Active Frame"
+    bl_description = "Delete all strokes in active frames"
+    bl_options = {"REGISTER"}
+
+    @classmethod
+    def poll(cls, context):
+        return context.object and context.object.type == 'GPENCIL'
+    
+    def execute(self, context):
+        obj = context.object
+        l = obj.data.layers.active
+        if not l:
+            self.report({'ERROR'}, 'No layers')
+            return {'CANCELLED'}
+        f = l.active_frame
+        if not f:
+            self.report({'ERROR'}, 'No active frame')
+            return {'CANCELLED'}
+
+        ct = len(f.strokes)
+        if not ct:
+            self.report({'ERROR'}, 'Active frame already empty')
+            return {'CANCELLED'}
+
+        for s in reversed(f.strokes):
+            f.strokes.remove(s)
+        self.report({'INFO'}, f'Cleared active frame ({ct} strokes removed)')
+        
+        return {'FINISHED'}
+
 classes = (
 GPTB_OT_copy_text,
 GPTB_OT_flipx_view,
@@ -458,6 +490,7 @@ GPTB_OT_set_view_as_cam,
 GPTB_OT_reset_cam_rot,
 GPTB_OT_toggle_mute_animation,
 GPTB_OT_list_disabled_anims,
+GPTB_OT_clear_active_frame,
 )
 
 def register():