fix(bmm): address CodeRabbit review feedback

- Improve retrospective status descriptions for clarity
- Fix empty epic detection to only warn on in-progress epics
- Add 'generated' to required metadata field validation

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

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/modules/bmm/workflows/4-implementation/sprint-planning/instructions.md

@@ -213,8 +213,8 @@ backlog → ready-for-dev → in-progress → review → done
 optional ↔ done
 ```
 
-- **optional**: Can be done but not required
-- **done**: Retrospective has been completed
+- **optional**: Ready to be conducted but not required
+- **done**: Finished
 
 ### Guidelines
 

src/modules/bmm/workflows/4-implementation/sprint-status/instructions.md

@@ -85,7 +85,7 @@ Enter corrections (e.g., "1=in-progress, 2=backlog") or "skip" to continue witho
 - IF all epics have status "backlog" AND no stories have status "ready-for-dev": prompt `/bmad:bmm:workflows:create-story`
 - IF `generated` timestamp is more than 7 days old: warn "sprint-status.yaml may be stale"
 - IF any story key doesn't match an epic pattern (e.g., story "5-1-..." but no "epic-5"): warn "orphaned story detected"
-- IF any epic has status != done but has no associated stories: warn "empty epic with no stories"
+- IF any epic has status in-progress but has no associated stories: warn "in-progress epic has no stories"
   </step>
 
 <step n="3" goal="Select next action recommendation">
@@ -194,7 +194,7 @@ If the command targets a story, set `story_key={{next_story_id}}` when prompted.
 
 <action>Read and parse {sprint_status_file}</action>
 
-<action>Validate required metadata fields exist: project, project_key, tracking_system, story_location</action>
+<action>Validate required metadata fields exist: generated, project, project_key, tracking_system, story_location</action>
 <check if="any required field missing">
 <template-output>is_valid = false</template-output>
 <template-output>error = "Missing required field(s): {{missing_fields}}"</template-output>