feat(workflows): add brownfield epic scoping to detect file churn (#1823)

Add design completeness gate, file overlap check, and validation
to prevent unnecessary file churn when epics target the same component.

src/bmm/workflows/3-solutioning/create-epics-and-stories/steps/step-02-design-epics.md

@@ -76,7 +76,8 @@ Load {outputFile} and review:
 2. **Requirements Grouping**: Group related FRs that deliver cohesive user outcomes
 3. **Incremental Delivery**: Each epic should deliver value independently
 4. **Logical Flow**: Natural progression from user's perspective
-5. **🔗 Dependency-Free Within Epic**: Stories within an epic must NOT depend on future stories
+5. **Dependency-Free Within Epic**: Stories within an epic must NOT depend on future stories
+6. **Implementation Efficiency**: Consider consolidating epics that all modify the same core files into fewer epics
 
 **⚠️ CRITICAL PRINCIPLE:**
 Organize by USER VALUE, not technical layers:
@@ -95,6 +96,18 @@ Organize by USER VALUE, not technical layers:
 - Epic 3: Frontend Components (creates reusable components) - **No user value**
 - Epic 4: Deployment Pipeline (CI/CD setup) - **No user value**
 
+**❌ WRONG Epic Examples (File Churn on Same Component):**
+
+- Epic 1: File Upload (modifies model, controller, web form, web API)
+- Epic 2: File Status (modifies model, controller, web form, web API)
+- Epic 3: File Access permissions (modifies model, controller, web form, web API)
+- All three epics touch the same files — consolidate into one epic with ordered stories
+
+**✅ CORRECT Alternative:**
+
+- Epic 1: File Management Enhancement (upload, status, permissions as stories within one epic)
+- Rationale: Single component, fully pre-designed, no feedback loop between epics
+
 **🔗 DEPENDENCY RULES:**
 
 - Each epic must deliver COMPLETE functionality for its domain
@@ -103,21 +116,38 @@ Organize by USER VALUE, not technical layers:
 
 ### 3. Design Epic Structure Collaboratively
 
-**Step A: Identify User Value Themes**
+**Step A: Assess Context and Identify Themes**
+
+First, assess how much of the solution design is already validated (Architecture, UX, Test Design).
+When the outcome is certain and direction changes between epics are unlikely, prefer fewer but larger epics.
+Split into multiple epics when there is a genuine risk boundary or when early feedback could change direction
+of following epics.
+
+Then, identify user value themes:
 
 - Look for natural groupings in the FRs
 - Identify user journeys or workflows
 - Consider user types and their goals
 
 **Step B: Propose Epic Structure**
-For each proposed epic:
+
+For each proposed epic (considering whether epics share the same core files):
 
 1. **Epic Title**: User-centric, value-focused
 2. **User Outcome**: What users can accomplish after this epic
 3. **FR Coverage**: Which FR numbers this epic addresses
 4. **Implementation Notes**: Any technical or UX considerations
 
-**Step C: Create the epics_list**
+**Step C: Review for File Overlap**
+
+Assess whether multiple proposed epics repeatedly target the same core files. If overlap is significant:
+
+- Distinguish meaningful overlap (same component end-to-end) from incidental sharing
+- Ask whether to consolidate into one epic with ordered stories
+- If confirmed, merge the epic FRs into a single epic, preserving dependency flow: each story must still fit within
+  a single dev agent's context
+
+**Step D: Create the epics_list**
 
 Format the epics_list as:
 

src/bmm/workflows/3-solutioning/create-epics-and-stories/steps/step-04-final-validation.md

@@ -110,6 +110,12 @@ Review the complete epic and story breakdown to ensure EVERY FR is covered:
 - Dependencies flow naturally
 - Foundation stories only setup what's needed
 - No big upfront technical work
+- **File Churn Check:** Do multiple epics repeatedly modify the same core files?
+  - Assess whether the overlap pattern suggests unnecessary churn or is incidental
+  - If overlap is significant: Validate that splitting provides genuine value (risk mitigation, feedback loops, context size limits)
+  - If no justification for the split: Recommend consolidation into fewer epics
+  - ❌ WRONG: Multiple epics each modify the same core files with no feedback loop between them
+  - ✅ RIGHT: Epics target distinct files/components, OR consolidation was explicitly considered and rejected with rationale
 
 ### 5. Dependency Validation (CRITICAL)