* docs: add workflows reference, reorganize into docs/reference/, and add --version flag
- Move integrations.md, extensions.md, presets.md into docs/reference/
- New docs/reference/workflows.md: command reference for all workflow
commands, built-in SDD Cycle workflow with Mermaid diagram, step types,
expressions, input types, state/resume, and FAQ
- Rename workflow input feature_name to spec with prompt 'Describe what
you want to build' to match speckit.specify command terminology
- Add --version / -V flag to root specify command with tests
- Update docs/toc.yml, README.md links, and docs/upgrade.md cross-reference
to use reference/ paths
- Add workflow command to README CLI reference table
* docs: update speckit_version requirement to >=0.7.2 in workflow example
