refactor: migrate agent system from XML tool calling to OpenAI SDK with native function calling

- Replace custom XML-based tool parsing (XMLToolExecutor) with OpenAI SDK's
  native tool_calls via `openai` npm package (dangerouslyAllowBrowser)
- Consolidate 4 LLM providers (OpenAI, Claude, Gemini, ClaudeOpenRouter)
  into a single OpenAI SDK-based LLMProvider compatible with any
  OpenAI-style API (OpenAI, OpenRouter, Ollama, vLLM)
- Move agentic tool execution loop from ChatBox into AgentCore
- Update Message type to support tool roles, tool_calls, and tool_call_id
- Update system prompt to remove XML formatting instructions (~45% smaller)
- Remove AttemptCompletionTool (replaced by stop_reason detection),
  ThinkTool, and ThinkingTool
- Polish tool descriptions for OpenAI function calling schema compliance
- Normalize base URLs by stripping /chat/completions suffix

src/utils/toolExecutionUtils.ts

@@ -1,102 +0,0 @@
-import { XMLToolExecutor } from '../agent/core/XMLToolExecutor';
-import { extractXMLFromString } from '../util/xmlUtil';
-import { createToolResultMessage } from './chatMessageUtils';
-import type { ChatMessage } from '../types/projectTypes';
-
-interface ToolExecutionResult {
-  success: boolean;
-  result: string;
-}
-
-interface ToolExecutionOptions {
-  onMessageAdd: (message: ChatMessage) => void;
-  onStatusUpdate: (status: string) => void;
-}
-
-export const extractActionableTools = (response: string): string[] => {
-  const xmlBlocks = extractXMLFromString(response);
-  // Consider only actionable tools (exclude think/thinking)
-  return xmlBlocks.filter((block) => {
-    const match = block.match(/<([a-zA-Z_][a-zA-Z0-9_-]*)/);
-    const name = match ? match[1].toLowerCase() : '';
-    return name !== 'think' && name !== 'thinking';
-  });
-};
-
-export const extractToolName = (xmlBlock: string): string => {
-  const toolNameMatch = xmlBlock.match(/<([a-zA-Z_][a-zA-Z0-9_-]*)/);
-  return toolNameMatch ? toolNameMatch[1] : 'unknown_tool';
-};
-
-export const executeSingleTool = async (
-  xmlBlock: string,
-  toolName: string,
-  options: ToolExecutionOptions
-): Promise<ToolExecutionResult> => {
-  const { onMessageAdd } = options;
-  
-  try {
-    const executor = XMLToolExecutor.instance();
-    const results = await executor.executeXMLTools(xmlBlock);
-    const result = results[0]; // Single block should give single result
-    
-    if (result) {
-      // Add friendly display message
-      const toolMessage = createToolResultMessage(toolName, result.success, result.result);
-      onMessageAdd(toolMessage);
-      
-      return {
-        success: result.success,
-        result: result.result
-      };
-    }
-    
-    return {
-      success: false,
-      result: 'No result returned from tool execution'
-    };
-  } catch (error) {
-    // Handle individual tool error
-    const errorMessage = `Tool execution failed: ${error}`;
-    const toolMessage = createToolResultMessage(toolName, false, errorMessage);
-    onMessageAdd(toolMessage);
-    
-    return {
-      success: false,
-      result: errorMessage
-    };
-  }
-};
-
-export const formatToolResultForLLM = (toolName: string, result: ToolExecutionResult): string => {
-  // Skip thinking tools
-  if (toolName === 'thinking' || toolName === 'think') {
-    return '';
-  }
-  
-  return `tool: ${toolName}\nsuccess: ${result.success}\nresult:\n${result.result}\n------------\n`;
-};
-
-export const executeAllTools = async (
-  actionableBlocks: string[],
-  options: ToolExecutionOptions
-): Promise<string> => {
-  const { onStatusUpdate } = options;
-  
-  onStatusUpdate(`Executing ${actionableBlocks.length} tool(s)...`);
-  
-  let accumulatedResults = '';
-  
-  // Execute tools sequentially with real-time updates
-  for (let i = 0; i < actionableBlocks.length; i++) {
-    onStatusUpdate(`Executing tool ${i + 1} of ${actionableBlocks.length}...`);
-    
-    const toolName = extractToolName(actionableBlocks[i]);
-    const result = await executeSingleTool(actionableBlocks[i], toolName, options);
-    
-    // Accumulate formatted result for LLM
-    accumulatedResults += formatToolResultForLLM(toolName, result);
-  }
-  
-  return accumulatedResults;
-};