fix(acp): advertise and forward image prompts

tests/acp_adapter/test_acp_images.py

@@ -0,0 +1,36 @@
+import pytest
+from acp.schema import ImageContentBlock, TextContentBlock
+
+from acp_adapter.server import HermesACPAgent, _content_blocks_to_openai_user_content
+
+
+def test_acp_image_blocks_convert_to_openai_multimodal_content():
+    content = _content_blocks_to_openai_user_content([
+        TextContentBlock(type="text", text="What is in this image?"),
+        ImageContentBlock(type="image", data="aGVsbG8=", mimeType="image/png"),
+    ])
+
+    assert content == [
+        {"type": "text", "text": "What is in this image?"},
+        {
+            "type": "image_url",
+            "image_url": {"url": "data:image/png;base64,aGVsbG8="},
+        },
+    ]
+
+
+def test_text_only_acp_blocks_stay_string_for_legacy_prompt_path():
+    content = _content_blocks_to_openai_user_content([
+        TextContentBlock(type="text", text="/help"),
+    ])
+
+    assert content == "/help"
+
+
+@pytest.mark.asyncio
+async def test_initialize_advertises_image_prompt_capability():
+    response = await HermesACPAgent().initialize()
+
+    assert response.agent_capabilities is not None
+    assert response.agent_capabilities.prompt_capabilities is not None
+    assert response.agent_capabilities.prompt_capabilities.image is True