feat: add canvas export to PNG via File menu, Cmd+Shift+E, and MCP tool

crates/agcanvas-mcp/src/tools.rs

@@ -203,6 +203,18 @@ pub struct RenderMermaidParam {
     pub height: Option<f32>,
 }
 
+#[derive(Debug, serde::Deserialize, schemars::JsonSchema)]
+pub struct ExportCanvasParam {
+    #[schemars(description = "Session ID to target. If omitted, uses the active session.")]
+    pub session_id: Option<String>,
+    #[schemars(description = "File path to save the PNG export to")]
+    pub path: String,
+    #[schemars(description = "Scale factor for the export (default 2.0 for high DPI)")]
+    pub scale: Option<f32>,
+    #[schemars(description = "Background color as hex e.g. '#1a1a2e' (default dark canvas color)")]
+    pub background: Option<String>,
+}
+
 #[derive(Debug, serde::Deserialize, schemars::JsonSchema)]
 pub struct BatchParam {
     #[schemars(
@@ -565,6 +577,29 @@ impl AgCanvasServer {
         self.call_agcanvas(&request).await
     }
 
+    #[tool(
+        description = "Export the canvas as a PNG image. Renders all layers (SVG, drawing elements) into a single image file."
+    )]
+    async fn export_canvas(
+        &self,
+        Parameters(params): Parameters<ExportCanvasParam>,
+    ) -> Result<CallToolResult, McpError> {
+        let mut request = serde_json::json!({
+            "type": "ExportCanvas",
+            "path": params.path,
+        });
+        if let Some(sid) = params.session_id {
+            request["session_id"] = serde_json::Value::String(sid);
+        }
+        if let Some(s) = params.scale {
+            request["scale"] = serde_json::json!(s);
+        }
+        if let Some(bg) = params.background {
+            request["background"] = serde_json::Value::String(bg);
+        }
+        self.call_agcanvas(&request).await
+    }
+
     #[tool(
         description = "Send multiple Augmented Canvas operations in one request. Accepts a JSON array of request objects and returns one response per operation in a BatchResult."
     )]