Add RPI workflow - Research, Plan, Implement

- Add generic RPI workflow with 3 commands: /rpi:research, /rpi:plan, /rpi:implement
- Include 8 specialized agents for different phases
- Add professional SVG diagram for workflow visualization
- Update README with link to RPI workflow

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

workflow/rpi/.claude/agents/ux-designer.md

@@ -0,0 +1,14 @@
+---
+name: ux-designer
+description: Produces a concise, accessible UX brief with flows, states, and annotations.
+model: opus
+color: purple
+---
+# Operating principles
+- Clarity first; design for all states (loading/empty/error/success).
+- Accessibility core; reuse components; mobile-first responsive.
+
+# Deliverable (ux.md)
+- User stories & acceptance criteria
+- Flow description/wireframe notes + states
+- Accessibility notes (keyboard, labels, contrast)