Render Mermaid diagrams and worktree images in agent Markdown

api/openapi.yaml

@@ -327,6 +327,30 @@ paths:
         "404": { $ref: "#/components/responses/Error" }
         "409": { $ref: "#/components/responses/Error" }
 
+  /api/tasks/{taskId}/image:
+    parameters:
+      - { name: taskId, in: path, required: true, schema: { type: string } }
+    get:
+      operationId: getTaskImage
+      description: >
+        An image file from the task's worktree, for Markdown images and image attachments. path is absolute or relative
+        to the worktree; after resolving symlinks it must be inside the worktree. PNG, JPEG, GIF, WebP and SVG, chosen by extension.
+      parameters:
+        - { name: path, in: query, required: true, schema: { type: string } }
+      responses:
+        "200":
+          description: The file's bytes.
+          content:
+            image/png: { schema: { type: string, format: binary } }
+            image/jpeg: { schema: { type: string, format: binary } }
+            image/gif: { schema: { type: string, format: binary } }
+            image/webp: { schema: { type: string, format: binary } }
+            image/svg+xml: { schema: { type: string, format: binary } }
+        "400": { $ref: "#/components/responses/Error" }
+        "403": { $ref: "#/components/responses/Error" }
+        "404": { $ref: "#/components/responses/Error" }
+        "409": { $ref: "#/components/responses/Error" }
+
   /api/tasks/{taskId}/diff:
     parameters:
       - { name: taskId, in: path, required: true, schema: { type: string } }
@@ -832,7 +856,7 @@ components:
       required: [kind]
       properties:
         kind: { type: string, enum: [file, diff, image, diagram, task, snapshot, url] }
-        path: { type: string, description: "file: repo-relative path." }
+        path: { type: string, description: "file: repo-relative path. image: an image file in the task's worktree, absolute or relative to it." }
         start_line: { type: integer }
         end_line: { type: integer }
         ref: { type: string, description: "diff: git revision range." }