fix(a2a): preserve streaming tool use content

[java-lbb]

AgentScope-Java Version

1.1.0-SNAPSHOT

Description

This PR fixes A2A conversion for streaming ToolUseBlock fragments.

Previously, ToolUseBlockParser serialized only ToolUseBlock#getInput() into DataPart.data. Streaming tool-call fragments can carry argument deltas in ToolUseBlock#getContent() while input and metadata are empty, so the raw content was dropped during A2A conversion.

Changes made:

• Add an internal DataPart.data key for raw streaming tool-use content.
• Preserve ToolUseBlock.content when converting ToolUseBlock to DataPart.
• Restore that content when converting DataPart back to ToolUseBlock.
• Keep the internal content key out of ToolUseBlock.input.
• Add regression tests for both conversion directions.

Test commands:

mvn -pl agentscope-extensions/agentscope-extensions-a2a/agentscope-extensions-a2a-client -am "-Dtest=ToolUseBlockParserTest#testParseStreamingToolUseContent,DataPartParserTest#testParseDataPartWithStreamingToolUseContent" test

mvn -pl agentscope-extensions/agentscope-extensions-a2a/agentscope-extensions-a2a-client -am test

Local results:

Tests run: 106, Failures: 0, Errors: 0, Skipped: 0
BUILD SUCCESS

Fixes #1526

Checklist

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

• Code has been formatted with mvn spotless:apply
• All related tests are passing
• Javadoc comments are complete and follow project conventions
• Related documentation has been updated (not needed for this bug fix)
• Code is ready for review

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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