refactor(agent-service): type ReActStep tool/message fields precisely

ReActStep used `unknown` for fields whose shapes we actually know:
- inputMessages -> ModelMessage[] (the prepared AI SDK messages)
- toolCalls[].input -> Record<string, unknown> (tool args are JSON objects)
- toolResults[].output -> string (every tool returns via createToolResult/createErrorResult)

The AI SDK types tc.input / tr.output as `unknown` for dynamically registered
tools, so narrow at the single construction boundary in texera-agent.ts.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: bobbai00

agent-service/src/agent/texera-agent.ts

@@ -571,15 +571,18 @@ export class TexeraAgent {
         onStepFinish: async ({ text, toolCalls, toolResults, usage }) => {
           stepIndex++;
 
+          // The AI SDK types tc.input / tr.output as `unknown` for dynamically
+          // registered tools; narrow to the shapes our tools actually produce
+          // (object args, string results — see tools/*).
           const formattedToolCalls = toolCalls?.map(tc => ({
             toolName: tc.toolName,
             toolCallId: tc.toolCallId,
-            input: tc.input,
+            input: tc.input as Record<string, unknown>,
           }));
 
           const formattedToolResults = toolResults?.map(tr => ({
             toolCallId: tr.toolCallId,
-            output: tr.output,
+            output: tr.output as string,
             isError: !!(tr.output as any)?.error,
           }));
 

agent-service/src/types/agent.ts

@@ -17,6 +17,7 @@
  * under the License.
  */
 
+import type { ModelMessage } from "ai";
 import type { WorkflowContent } from "./workflow";
 
 export enum AgentState {
@@ -48,15 +49,15 @@ export interface ReActStep {
   toolCalls?: Array<{
     toolName: string;
     toolCallId: string;
-    input: unknown;
+    input: Record<string, unknown>;
   }>;
   toolResults?: Array<{
     toolCallId: string;
-    output: unknown;
+    output: string;
     isError?: boolean;
   }>;
   usage?: TokenUsage;
-  inputMessages?: unknown[];
+  inputMessages?: ModelMessage[];
   messageSource?: "chat" | "feedback";
   beforeWorkflowContent?: WorkflowContent;
   afterWorkflowContent?: WorkflowContent;