align dev-story skill references with upstream patterns

src/bmm/agents/dev.agent.yaml

@@ -30,7 +30,7 @@ agent:
 
   menu:
     - trigger: DS or fuzzy match on dev-story
-      exec: "{project-root}/_bmad/bmm/workflows/4-implementation/bmad-dev-story/workflow.md"
+      exec: "skill:bmad-dev-story"
       description: "[DS] Dev Story: Write the next or specified stories tests and code."
 
     - trigger: CR or fuzzy match on code-review

src/bmm/workflows/4-implementation/bmad-dev-story/workflow.md

@@ -32,7 +32,6 @@ Load config from `{project-root}/_bmad/bmm/config.yaml` and resolve:
 
 ### Paths
 
-- `installed_path` = `.`
 - `validation` = `./checklist.md`
 - `story_file` = `` (explicit story path; auto-discovered if empty)
 - `sprint_status` = `{implementation_artifacts}/sprint-status.yaml`