fix(bmm): complete cleanup of epic-tech-context workflow removal (#1001)

- Remove references to deprecated epic-tech-context, story-context,
  validate-epic-tech-context, validate-story-context, and story-done workflows
- Simplify epic status: backlog → in-progress → done (was backlog → contexted)
- Update create-story to handle legacy 'contexted' status for backward compat
- Clean up sprint-planning instructions and status template
- Update docs: agents-guide, brownfield-guide, faq, glossary, quick-start

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

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

src/modules/bmm/workflows/4-implementation/retrospective/instructions.md

@@ -1395,9 +1395,9 @@ Retrospective document was saved successfully, but {sprint_status_file} may need
 - Do NOT start Epic {{next_epic_num}} until review is complete
   {{else}}
 
-4. **Begin Epic {{next_epic_num}} planning when preparation complete**
-   - Load PM agent and run `epic-tech-context` for Epic {{next_epic_num}}
-   - Or continue with existing contexted epics
+4. **Begin Epic {{next_epic_num}} when ready**
+   - Start drafting stories with SM agent's `create-story`
+   - Epic will be marked as `in-progress` automatically when first story is created
    - Ensure all critical path items are done first
      {{/if}}