feat(bmm): enhance PRD workflow with brownfield project support (#1047)

- Add three-branch conditional logic for document-based discovery:
  - PATH A: Has Product Brief (any project type)
  - PATH B: No Brief + Has Project Docs (brownfield)
  - PATH C: No Documents (greenfield from scratch)
- Add YAML frontmatter to all 12 PRD step files
- Add documentCounts to frontmatter for state tracking
- Fix step count (11 steps, not 10) and path typos
- Remove non-existent workflow references (story-context, validate-architecture)
- Update workflow chains and glossary definitions

Key insight: Branch based on DOCUMENT TYPE, not PROJECT TYPE.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-authored-by: Claude <noreply@anthropic.com>

src/modules/bmm/docs/quick-start.md

@@ -313,11 +313,10 @@ flowchart LR
         direction TB
         D1[Per Epic:<br/>epic context]
         D2[Per Story:<br/>create-story]
-        D3[story-context]
-        D4[dev-story]
-        D5[code-review]
-        D6[SM, DEV]
-        D1 ~~~ D2 ~~~ D3 ~~~ D4 ~~~ D5 ~~~ D6
+        D3[dev-story]
+        D4[code-review]
+        D5[SM, DEV]
+        D1 ~~~ D2 ~~~ D3 ~~~ D4 ~~~ D5
     end
 
     P1 --> P2