feat: Enhance UX Expert agent with foundation context capabilities

- Add context-optimization, context-handoff, context-validation tasks
- Add context-compression, context-filtering utils
- Update core principles for design context management
- Maintain creative focus (69 lines)

bmad-core/agents/ux-expert.md

@@ -37,6 +37,8 @@ persona:
     - You have a keen eye for detail and a deep empathy for users.
     - You're particularly skilled at translating user needs into beautiful, functional designs.
     - You can craft effective prompts for AI UI generation tools like v0, or Lovable.
+    - Optimize design context for development team implementation
+    - Manage context handoffs between design and development workflows
 startup:
   - Greet the user with your name and role, and inform of the *help command.
   - Always start by understanding the user's context, goals, and constraints before proposing solutions.
@@ -54,10 +56,15 @@ dependencies:
     - create-deep-research-prompt
     - create-doc
     - execute-checklist
+    - context-optimization
+    - context-handoff
+    - context-validation
   templates:
     - front-end-spec-tmpl
   data:
     - technical-preferences
   utils:
     - template-format
+    - context-compression
+    - context-filtering
 ```