fix(ReActAgent): allow tool calls to reach acting phase for proper error feedback(#850)

…ror feedback

When model generates tool calls that don't exist in toolkit, the
isFinished() method was prematurely terminating the ReAct loop,
preventing the model from receiving error feedback.

Now tool calls (even non-existent ones) proceed to the acting phase
where ToolExecutor returns 'Tool not found' error. This allows the model
to see the error in memory and self-correct in the next iteration.

Simplified isFinished() to only check if there are tool calls, removing
the toolkit existence check since error handling is already properly
implemented in ToolExecutor.executeCore().

## AgentScope-Java Version

[The version of AgentScope-Java you are working on, e.g. 1.0.9, check
your pom.xml dependency version or run `mvn dependency:tree | grep
agentscope-parent:pom`(only mac/linux)]

## Description

[Please describe the background, purpose, changes made, and how to test
this PR]

## Checklist

Please check the following items before code is ready to be reviewed.

- [x]  Code has been formatted with `mvn spotless:apply`
- [x]  All tests are passing (`mvn test`)
- [x]  Javadoc comments are complete and follow project conventions
- [x] Related documentation has been updated (e.g. links, examples,
etc.)
- [x]  Code is ready for review

Co-authored-by: LearningGp <learninggp4.74@gmail.com>

Author: luoxiner

agentscope-core/src/main/java/io/agentscope/core/ReActAgent.java

@@ -750,12 +750,9 @@ private boolean isFinished(Msg msg) {
         List<ToolUseBlock> toolCalls = msg.getContentBlocks(ToolUseBlock.class);
 
         // No tool calls - finished
-        if (toolCalls.isEmpty()) {
-            return true;
-        }
-
-        // Has tool calls but none are in toolkit - finished
-        return toolCalls.stream().noneMatch(tc -> toolkit.getTool(tc.getName()) != null);
+        // If there are tool calls (even non-existent ones), continue to acting phase
+        // where ToolExecutor will return "Tool not found" error for the model to see
+        return toolCalls.isEmpty();
     }
 
     /**