Fix delete_image: POST with images JSON array (DevTools-confirmed format)

DSM Container Manager rejects name+tag and sha256 id params (error 114).
Browser DevTools capture shows the correct call is:

  POST SYNO.Docker.Image / delete / version=1
  images=[{"repository":"nouchka/sqlite3","tags":["latest"]}]

Changes:
- Add DsmClient.post_request() for form-encoded POST requests
- delete_image now calls post_request with version=1 and the images
  JSON array built from the resolved repository name and tag
- Remove unused docker error-code dict from _error_message()
- Tests mock post_request and assert the images param content

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

tests/test_modules/test_images.py

@@ -203,17 +203,18 @@ async def test_delete_image_preview():
 
 @pytest.mark.asyncio
 async def test_delete_image_confirmed():
+    import json
+
     from mcp_synology_container.modules.images import register_images
 
     client = AsyncMock()
+    client.post_request = AsyncMock(return_value={})
 
     async def mock_request(api, method, **kwargs):
         if api == "SYNO.Docker.Image" and method == "list":
             return SAMPLE_IMAGES
         if api == "SYNO.Docker.Container":
             return {"containers": []}
-        if api == "SYNO.Docker.Image" and method == "delete":
-            return {}
         return {}
 
     client.request.side_effect = mock_request
@@ -225,12 +226,11 @@ async def test_delete_image_confirmed():
     assert "redis:7" in result
     assert "freed" in result
 
-    # Delete must use the sha256 id, not name+tag
-    delete_call = next(c for c in client.request.call_args_list if c.args[1] == "delete")
-    params = delete_call.kwargs.get("params") or {}
-    assert params.get("id") == "sha256:cccc"
-    assert "name" not in params
-    assert "tag" not in params
+    # post_request must be called with images JSON param, not name/tag/id
+    client.post_request.assert_called_once()
+    params = client.post_request.call_args.kwargs.get("params", {})
+    images = json.loads(params["images"])
+    assert images == [{"repository": "redis", "tags": ["7"]}]
 
 
 @pytest.mark.asyncio
@@ -238,6 +238,7 @@ async def test_delete_image_not_found():
     from mcp_synology_container.modules.images import register_images
 
     client = AsyncMock()
+    client.post_request = AsyncMock(return_value={})
 
     async def mock_request(api, method, **kwargs):
         if api == "SYNO.Docker.Image" and method == "list":
@@ -250,6 +251,7 @@ async def test_delete_image_not_found():
 
     result = await tools["delete_image"](image_id="nonexistent:latest", confirmed=True)
     assert "not found" in result
+    client.post_request.assert_not_called()
 
 
 @pytest.mark.asyncio
@@ -257,6 +259,7 @@ async def test_delete_image_in_use_blocked():
     from mcp_synology_container.modules.images import register_images
 
     client = AsyncMock()
+    client.post_request = AsyncMock(return_value={})
 
     async def mock_request(api, method, **kwargs):
         if api == "SYNO.Docker.Image" and method == "list":
@@ -272,21 +275,23 @@ async def test_delete_image_in_use_blocked():
     result = await tools["delete_image"](image_id="nginx:1.24", confirmed=True)
     assert "Cannot delete" in result
     assert "my-nginx" in result
+    client.post_request.assert_not_called()
 
 
 @pytest.mark.asyncio
 async def test_delete_image_by_hash():
+    import json
+
     from mcp_synology_container.modules.images import register_images
 
     client = AsyncMock()
+    client.post_request = AsyncMock(return_value={})
 
     async def mock_request(api, method, **kwargs):
         if api == "SYNO.Docker.Image" and method == "list":
             return SAMPLE_IMAGES
         if api == "SYNO.Docker.Container":
             return {"containers": []}
-        if api == "SYNO.Docker.Image" and method == "delete":
-            return {}
         return {}
 
     client.request.side_effect = mock_request
@@ -297,10 +302,18 @@ async def test_delete_image_by_hash():
     assert "Deleted" in result
     assert "redis" in result
 
+    # Verify images param uses the resolved name+tag (not the hash)
+    call_kwargs = client.post_request.call_args
+    params = call_kwargs.kwargs.get("params") or {}
+    images = json.loads(params.get("images", "[]"))
+    assert images == [{"repository": "redis", "tags": ["7"]}]
+
 
 @pytest.mark.asyncio
 async def test_delete_image_registry_prefixed_name():
     """Registry-prefixed image names (e.g. ghcr.io/foo/bar:v1) must split at last ':'."""
+    import json
+
     from mcp_synology_container.modules.images import register_images
 
     registry_images = {
@@ -317,14 +330,13 @@ async def test_delete_image_registry_prefixed_name():
     }
 
     client = AsyncMock()
+    client.post_request = AsyncMock(return_value={})
 
     async def mock_request(api, method, **kwargs):
         if api == "SYNO.Docker.Image" and method == "list":
             return registry_images
         if api == "SYNO.Docker.Container":
             return {"containers": []}
-        if api == "SYNO.Docker.Image" and method == "delete":
-            return {}
         return {}
 
     client.request.side_effect = mock_request
@@ -337,12 +349,11 @@ async def test_delete_image_registry_prefixed_name():
     assert "Deleted" in result
     assert "open-webui" in result
 
-    # Verify delete was called with the sha256 ID, not name+tag
-    delete_call = next(c for c in client.request.call_args_list if c.args[1] == "delete")
-    params = delete_call.kwargs.get("params") or {}
-    assert params.get("id") == "sha256:dddd"
-    assert "name" not in params
-    assert "tag" not in params
+    # images param must use full registry-prefixed repository name
+    call_kwargs = client.post_request.call_args
+    params = call_kwargs.kwargs.get("params") or {}
+    images = json.loads(params.get("images", "[]"))
+    assert images == [{"repository": "ghcr.io/open-webui/open-webui", "tags": ["v0.8.10"]}]
 
 
 @pytest.mark.asyncio
@@ -351,14 +362,13 @@ async def test_delete_image_api_error():
     from mcp_synology_container.modules.images import register_images
 
     client = AsyncMock()
+    client.post_request = AsyncMock(side_effect=SynologyError("delete failed", code=114))
 
     async def mock_request(api, method, **kwargs):
         if api == "SYNO.Docker.Image" and method == "list":
             return SAMPLE_IMAGES
         if api == "SYNO.Docker.Container":
             return {"containers": []}
-        if api == "SYNO.Docker.Image" and method == "delete":
-            raise SynologyError("delete failed", code=1)
         return {}
 
     client.request.side_effect = mock_request
@@ -367,6 +377,7 @@ async def test_delete_image_api_error():
 
     result = await tools["delete_image"](image_id="redis:7", confirmed=True)
     assert "Error" in result
+    assert "114" in result
 
 
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