Use raw agent names (e.g., 'dev', 'pm') for the name field in .agent.md
frontmatter and all agent references in prompt frontmatter, instead of
persona display names. This provides clean @mention and /command names.
Resolve Create Story / Validate Story filename collision where both
entries shared command 'bmad-bmm-create-story'. When multiple entries
share a command, derive unique filenames from the entry name slug.
Also pass workflow options (Create Mode, Validate Mode) to the prompt
body so each prompt invokes the correct workflow mode.
Fixes#1794
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>