Handle ollama's deviation from the OpenAI tool streaming spec (#1512)

The canonical sequence of tool streaming chunks according to OpenAI
documentation looks like this:

```json
[{"index": 0, "id": "call_DdmO9pD3xa9XTPNJ32zg2hcA", "function": {"arguments": "", "name": "get_weather"}, "type": "function"}]
[{"index": 0, "id": null, "function": {"arguments": "{\"", "name": null}, "type": null}]
[{"index": 0, "id": null, "function": {"arguments": "location", "name": null}, "type": null}]
[{"index": 0, "id": null, "function": {"arguments": "\":\"", "name": null}, "type": null}]
[{"index": 0, "id": null, "function": {"arguments": "Paris", "name": null}, "type": null}]
[{"index": 0, "id": null, "function": {"arguments": ",", "name": null}, "type": null}]
[{"index": 0, "id": null, "function": {"arguments": " France", "name": null}, "type": null}]
[{"index": 0, "id": null, "function": {"arguments": "\"}", "name": null}, "type": null}]
null
```

In ollama's case (tested on `llama3.2:3b` at least) the sequence of
chunks is different, the first chunk can already contain the `arguments`
string.

```
<Tool call_uiutvfya>
task_complete {}
```

This should close #1502

Author: julien-c

packages/mcp-client/package.json

@@ -34,7 +34,7 @@
 		"prepare": "pnpm run build",
 		"test": "vitest run",
 		"check": "tsc",
-		"agent": "tsx cli.ts"
+		"cli": "tsx cli.ts"
 	},
 	"files": [
 		"src",

packages/mcp-client/src/McpClient.ts

@@ -160,13 +160,18 @@ export class McpClient {
 			for (const toolCall of delta.tool_calls ?? []) {
 				// aggregating chunks into an encoded arguments JSON object
 				if (!finalToolCalls[toolCall.index]) {
+					/// first chunk of the tool call
 					finalToolCalls[toolCall.index] = toolCall;
-				}
-				if (finalToolCalls[toolCall.index].function.arguments === undefined) {
-					finalToolCalls[toolCall.index].function.arguments = "";
-				}
-				if (toolCall.function.arguments) {
-					finalToolCalls[toolCall.index].function.arguments += toolCall.function.arguments;
+
+					/// ensure .function.arguments is always a string
+					if (finalToolCalls[toolCall.index].function.arguments === undefined) {
+						finalToolCalls[toolCall.index].function.arguments = "";
+					}
+				} else {
+					/// any subsequent chunk to the same tool call
+					if (toolCall.function.arguments) {
+						finalToolCalls[toolCall.index].function.arguments += toolCall.function.arguments;
+					}
 				}
 			}
 			if (opts.exitIfFirstChunkNoTool && numOfChunks <= 2 && Object.keys(finalToolCalls).length === 0) {