fix(skills): normalize sprint planning native skill refs

Author: alexeyv

src/bmm/agents/sm.agent.yaml

@@ -20,7 +20,7 @@ agent:
 
   menu:
     - trigger: SP or fuzzy match on sprint-planning
-      exec: "{project-root}/_bmad/bmm/workflows/4-implementation/bmad-sprint-planning/workflow.md"
+      exec: "skill:bmad-sprint-planning"
       description: "[SP] Sprint Planning: Generate or update the record that will sequence the tasks to complete the full project that the dev agent will follow"
 
     - trigger: CS or fuzzy match on create-story

src/bmm/workflows/4-implementation/bmad-sprint-planning/workflow.md

@@ -1,8 +1,3 @@
----
-name: bmad-sprint-planning
-description: 'Generate sprint status tracking from epics. Use when the user says "run sprint planning" or "generate sprint plan"'
----
-
 # Sprint Planning Workflow
 
 **Goal:** Generate sprint status tracking from epics, detecting current story statuses and building a complete sprint-status.yaml file.