[feature/openrouter-provider] Refactor finish reason handling and tool call logic in agent and OpenAI provider

- Simplified finish reason check in `agent.go` by removing redundant variable assignment.
- Updated `openai.go` to override the finish reason to `FinishReasonToolUse` when tool calls are present.
- Ensured consistent finish reason handling in both `send` and `stream` methods of the OpenAI provider.

Author: isaac-scarrott

internal/llm/agent/agent.go

@@ -228,8 +228,7 @@ func (a *agent) processGeneration(ctx context.Context, sessionID, content string
 			return a.err(fmt.Errorf("failed to process events: %w", err))
 		}
 		logging.Info("Result", "message", agentMessage.FinishReason(), "toolResults", toolResults)
-		finishReason := agentMessage.FinishReason()
-		if (finishReason == message.FinishReasonToolUse || finishReason == message.FinishReasonUnknown) && toolResults != nil {
+		if (agentMessage.FinishReason() == message.FinishReasonToolUse) && toolResults != nil {
 			// We are not done, we need to respond with the tool response
 			msgHistory = append(msgHistory, agentMessage, *toolResults)
 			continue

internal/llm/provider/openai.go

@@ -204,11 +204,18 @@ func (o *openaiClient) send(ctx context.Context, messages []message.Message, too
 			content = openaiResponse.Choices[0].Message.Content
 		}
 
+		toolCalls := o.toolCalls(*openaiResponse)
+		finishReason := o.finishReason(string(openaiResponse.Choices[0].FinishReason))
+
+		if len(toolCalls) > 0 {
+			finishReason = message.FinishReasonToolUse
+		}
+
 		return &ProviderResponse{
 			Content:      content,
-			ToolCalls:    o.toolCalls(*openaiResponse),
+			ToolCalls:    toolCalls,
 			Usage:        o.usage(*openaiResponse),
-			FinishReason: o.finishReason(string(openaiResponse.Choices[0].FinishReason)),
+			FinishReason: finishReason,
 		}, nil
 	}
 }
@@ -267,13 +274,24 @@ func (o *openaiClient) stream(ctx context.Context, messages []message.Message, t
 			err := openaiStream.Err()
 			if err == nil || errors.Is(err, io.EOF) {
 				// Stream completed successfully
+				eventChan <- ProviderEvent{
+					Type: EventContentStop,
+				}
+
+				finishReason := o.finishReason(string(acc.ChatCompletion.Choices[0].FinishReason))
+
+				// Override finish reason to tool_use if there are tool calls
+				if len(toolCalls) > 0 {
+					finishReason = message.FinishReasonToolUse
+				}
+
 				eventChan <- ProviderEvent{
 					Type: EventComplete,
 					Response: &ProviderResponse{
 						Content:      currentContent,
 						ToolCalls:    toolCalls,
 						Usage:        o.usage(acc.ChatCompletion),
-						FinishReason: o.finishReason(string(acc.ChatCompletion.Choices[0].FinishReason)),
+						FinishReason: finishReason,
 					},
 				}
 				close(eventChan)