Add Mermaid Diagrams plugin

[omar-nahhas]

Adds plugins/mermaid_diagrams/index.yaml.

Renders Mermaid code blocks as interactive SVG diagrams in the chat UI (flowcharts, sequence, class/ER, state, mindmaps, timelines), with a click-to-zoom viewer. Ships a skill teaching the agent Mermaid syntax plus a behavioural nudge to reach for a diagram when a visual explanation helps.

• Repo: https://github.com/agent-zero-plugins/agent-zero-plugin-mermaid-diagrams (public, Apache-2.0)
• Root plugin.yaml has name: mermaid_diagrams, matching the folder name
• No thumbnail included: the upstream asset is a 16x16 placeholder, so the auto-generated fallback will look better

[a0-bot]

Plugin submission validation failed

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