Preferred method for creating diagram elements from Mermaid. ⚠️ IMPORTANT: Call get_guide first and follow its instructions! Use this tool for NEW diagrams and LARGE changes to existing diagrams whenever the request can be represented in Mermaid. Prefer translating the request into Mermaid instead of manually recreating it with add_elements. If room_id is NOT provided - creates a NEW canvas and returns url plus room_id. If the user did not explicitly mention an existing board/canvas/room, do NOT ask for a room_id; create a new canvas instead. If a previous Canvs tool result or assistant message in the same conversation contains a room_id, reuse it for follow-up requests like 'add to it' or 'same board'. If you only have a room URL, extract room_id from https://[host]/?room=[room_id] or https://[host]/gdrive?id=[room_id]. If the user refers to a previous board but no usable room_id is available, create a new canvas instead of asking for the URL by default. If room_id IS provided - adds diagram elements to that canvas. If the canvas is displayed as an inline widget in the interface, do NOT include the url in your reply. If no widget is shown, share the url so the user can open the canvas.Supports: flowchart, graph, flowchart-elk, sequenceDiagram, classDiagram, classDiagram-v2, stateDiagram, stateDiagram-v2, erDiagram, journey, gantt, pie, gitGraph, mindmap, timeline, C4Context, C4Container, C4Component, C4Dynamic, C4Deployment, sankey, sankey-beta, quadrantChart, xychart, xychart-beta, requirement, requirementDiagram, kanban, architecture, block, block-beta, packet, packet-beta, radar-beta, treemap, info. Example: "flowchart TD\n A[Start] --> B{Decision}\n B -->|Yes| C[OK]\n B -->|No| D[Cancel]"