Converts all ./step-XX.md, step-XX.md, and steps/step-XX.md
backtick references in new-format workflow and step files to
full {project-root}/_bmad/... paths.
Refs #1718
The PRD workflow step-02 was refactored to be discovery-only with
forward references to steps 2b and 2c, but those files were never
created. This left a gap where the workflow jumped from classification
directly to success criteria with no executive summary generation.
- Add step-02b-vision.md: collaborative vision/differentiator discovery
- Add step-02c-executive-summary.md: generate and append exec summary
- Update step-02 nextStepFile to chain through 02b instead of skipping to 03
Alex Verkhovsky