feat: add _meta row for bmad-help llms.txt integration

skills/module-help.csv

@@ -1,4 +1,5 @@
 module,skill,display-name,menu-code,description,action,args,phase,after,before,required,output-location,outputs
+BMad Builder,_meta,,,,,,,,,false,https://bmad-builder-docs.bmad-method.org/llms.txt,
 BMad Builder,bmad-bmb-setup,Setup Builder Module,SB,"Install or update BMad Builder module config and help entries.",configure,"{-H: headless mode}|{inline values: skip prompts with provided values}",anytime,,,false,{project-root}/_bmad,config.yaml and config.user.yaml
 BMad Builder,bmad-agent-builder,Build an Agent,BA,"Create, edit, or rebuild an agent skill through conversational discovery.",build-process,"{-H: headless mode}|{description: initial agent concept}|{path: existing agent to edit or rebuild}",anytime,,bmad-agent-builder:quality-analysis,false,bmad_builder_output_folder,agent skill
 BMad Builder,bmad-agent-builder,Analyze an Agent,AA,"Run quality analysis on an existing agent — structure, cohesion, prompt craft, and enhancement opportunities.",quality-analysis,"{-H: headless mode}|{path: agent to analyze}",anytime,bmad-agent-builder:build-process,,false,bmad_builder_reports,quality report