refactor(ai): improve error handling and stop reason types

- Add 'aborted' as a distinct stop reason separate from 'error'
- Change AssistantMessage.error to errorMessage for clarity
- Update error event to include reason field ('error' | 'aborted')
- Map provider-specific safety/refusal reasons to 'error' stop reason
- Reorganize utility functions into utils/ directory
- Rename agent.ts to agent-loop.ts for better clarity
- Fix error handling in all providers to properly distinguish abort from error

packages/ai/src/validation.ts

@@ -1,42 +0,0 @@
-import AjvModule from "ajv";
-import addFormatsModule from "ajv-formats";
-
-// Handle both default and named exports
-const Ajv = (AjvModule as any).default || AjvModule;
-const addFormats = (addFormatsModule as any).default || addFormatsModule;
-
-import type { Tool, ToolCall } from "./types.js";
-
-// Create a singleton AJV instance with formats
-const ajv = new Ajv({ allErrors: true, strict: false });
-addFormats(ajv);
-
-/**
- * Validates tool call arguments against the tool's TypeBox schema
- * @param tool The tool definition with TypeBox schema
- * @param toolCall The tool call from the LLM
- * @returns The validated arguments
- * @throws Error with formatted message if validation fails
- */
-export function validateToolArguments(tool: Tool, toolCall: ToolCall): any {
-	// Compile the schema
-	const validate = ajv.compile(tool.parameters);
-
-	// Validate the arguments
-	if (validate(toolCall.arguments)) {
-		return toolCall.arguments;
-	}
-
-	// Format validation errors nicely
-	const errors =
-		validate.errors
-			?.map((err: any) => {
-				const path = err.instancePath ? err.instancePath.substring(1) : err.params.missingProperty || "root";
-				return `  - ${path}: ${err.message}`;
-			})
-			.join("\n") || "Unknown validation error";
-
-	const errorMessage = `Validation failed for tool "${toolCall.name}":\n${errors}\n\nReceived arguments:\n${JSON.stringify(toolCall.arguments, null, 2)}`;
-
-	throw new Error(errorMessage);
-}