refactor: Major v6 epic creation improvements and documentation overhaul

## Key Changes

### 1. Epic Creation Workflow Enhancements
- Added user-value focused epic structure principles (NO technical layer breakdown)
- Implemented multi-mode detection: CONTINUE, REPLACE, or UPDATE existing epics
- Added comprehensive anti-pattern examples showing wrong vs right epic breakdown
- Epics now created AFTER architecture for technically-informed story breakdown
- Added checkpoint protocol for interactive workflow progression

### 2. Removed Deprecated Solutioning Gate Check
- Deleted entire solutioning-gate-check workflow (682 lines)
- Replaced by new implementation-readiness workflow
- Cleaner separation of concerns in solutioning phase

### 3. PRD Template Simplification
- Removed hardcoded "Implementation Planning", "References", and "Next Steps" sections
- PRD now focuses purely on requirements, not workflow orchestration
- Epics/stories created as separate step after architecture

### 4. Documentation Overhaul (15+ docs updated)
- Updated quick-start guide with v6 workflow sequence
- Clarified that epics are created AFTER architecture, not during PRD
- Updated solutioning docs to reflect implementation-readiness pattern
- Improved agents-guide, brownfield-guide, enterprise docs
- Enhanced glossary, FAQ, and workflow reference documentation

### 5. Workflow Path Adjustments
- All 4 paths updated (enterprise/method × brownfield/greenfield)
- Version bumps across BMGD, BMM, and CIS workflow YAMLs
- Minor instruction file updates for consistency

### Files Changed
- 65 files total: 468 insertions, 978 deletions (net reduction of 510 lines)
- 4 files deleted (entire solutioning-gate-check workflow)
- 1 new directory added (implementation-readiness placeholder)

src/modules/bmm/agents/architect.agent.yaml

@@ -28,9 +28,9 @@ agent:
       checklist: "{project-root}/{bmad_folder}/bmm/workflows/3-solutioning/architecture/checklist.md"
       description: Validate Architecture Document
 
-    - trigger: solutioning-gate-check
-      workflow: "{project-root}/{bmad_folder}/bmm/workflows/3-solutioning/solutioning-gate-check/workflow.yaml"
-      description: Validate solutioning is complete
+    - trigger: implementation-readiness
+      workflow: "{project-root}/{bmad_folder}/bmm/workflows/3-solutioning/implementation-readiness/workflow.yaml"
+      description: Validate implementation readiness - PRD, UX, Architecture, Epics aligned
 
     - trigger: party-mode
       workflow: "{project-root}/{bmad_folder}/core/workflows/party-mode/workflow.yaml"