Update LFM kernel backlog items - complete code review, start design phase

backlog/features/2025-08-15_design-modern-lfm-kernel.md

@@ -1,7 +1,7 @@
 ---
 id: "design-modern-lfm-kernel"
 title: "Design modern LFM kernel architecture"
-status: "Proposed"
+status: "In Progress"
 priority: "High"
 created: "2025-08-15"
 last_updated: "2025-08-15"
@@ -38,8 +38,8 @@ Design a modern LFM kernel implementation that follows GPy's current architectur
 - [ ] Design parameter handling for mass, damper, spring, sensitivity, delay
 - [ ] Plan integration with GPy's multioutput framework
 - [ ] Design cross-kernel computation methods
-- [ ] Plan parameter tying and constraint handling
 - [ ] Design efficient computation methods for large datasets
+- [x] Plan parameter tying and constraint handling (assumed to be addressed separately)
 
 ## Acceptance Criteria
 - [ ] Complete design specification document
@@ -50,10 +50,20 @@ Design a modern LFM kernel implementation that follows GPy's current architectur
 
 ## Implementation Notes
 - Study how other multioutput kernels in GPy handle output indices
-- Consider parameter tying approaches from MATLAB implementation
 - Design for extensibility to different differential equation types
 - Plan for efficient computation of cross-kernel terms
+- **Parameter Tying**: Assumed to be addressed by separate CIP-0002 work
+- **Design Focus**: Clean LFM implementation without parameter tying workarounds
 
 ## Related
 - CIP: 0001 (LFM kernel implementation)
 - Backlog: lfm-kernel-code-review
+
+## Progress Updates
+
+### 2025-08-15
+Design task started after completion of code review:
+- Code review identified parameter tying as a fundamental limitation
+- Decision made to proceed with clean LFM implementation assuming parameter tying addressed separately
+- Focus on core LFM functionality without parameter tying workarounds
+- Ready to begin detailed design of modern LFM kernel architecture