fix: handle tool execution timeout/error causing IllegalStateExceptio…

[chensk0601]

…n (#951)

ReActAgent throws IllegalStateException when tool calls timeout or fail, because no tool result is written to memory, leaving orphaned pending tool call states that crash the agent on subsequent requests.

Root cause:

• Tool execution timeout/error propagates without writing results to memory
• Pending tool call state remains, blocking subsequent doCall() invocations
• validateAndAddToolResults() throws when user message has no tool results

Changes:

• doCall(): detect pending tool calls without user-provided results and auto-generate error results to clear the pending state
• executeToolCalls(): add onErrorResume to catch tool execution failures and generate error tool results instead of propagating exceptions
• Add generateAndAddErrorToolResults() helper to create error results for orphaned pending tool calls

This ensures the agent recovers gracefully from tool failures instead of crashing, and the model receives proper error feedback to continue processing.

Closes #951

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.

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

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[codecov]

Codecov Report

❌ Patch coverage is 61.40351% with 22 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
...e/src/main/java/io/agentscope/core/ReActAgent.java	61.40%	19 Missing and 3 partials ⚠️

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