expression-visualize

Create Mermaid diagrams with light/dark compatible themes to visualize data flow, relationships, and conceptual structures. Use when: (1) explaining architecture or flow involving multiple components interacting across boundaries, (2) documenting a decision where showing structure or relationships will clarify the rationale, (3) reviewing code where change impact spans multiple files or layers and sequence matters, (4) onboarding someone to a complex part of the system where visual navigation helps, (5) prose descriptions of structure become long enough that a diagram would be clearer, (6) surfacing implicit assumptions about relationships or flow for team discussion, (7) planning a refactoring and comparing before/after state across approaches, (8) PR discussions would benefit from visualization to resolve ambiguity faster than comments