fix(extensions): preserve ReAct structure in current round compression to prevent infinite loops

[jujn]

Description

Close #1026
This PR fixes an issue where Strategy 6 compression destroyed the ReAct structure by squashing tool calls into a single text message, causing the LLM to fall into an infinite loop. It now preserves the ToolUse and ToolResult pairs using token-saving placeholders, safely injecting the final summary into the last tool result through a streamlined ContentBlock extraction.

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

[Copilot]

Pull request overview

This PR addresses AutoContextMemory Strategy 6 (“current round” compression) breaking ReAct semantics by ensuring tool-use/tool-result structure is preserved during compression, preventing repeated tool calls (infinite loops).

Changes:

• Updates Strategy 6 replacement logic to keep ToolUse / ToolResult message pairs and inject the LLM summary into the last ToolResult.
• Adjusts and adds unit tests to assert ReAct structure preservation and that the summary/offload hint lands in the final ToolResult.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 4 comments.

File	Description
agentscope-extensions/agentscope-extensions-autocontext-memory/src/main/java/io/agentscope/core/memory/autocontext/AutoContextMemory.java	Reworks Strategy 6 message replacement to preserve tool message structure and inject summary into last tool result.
agentscope-extensions/agentscope-extensions-autocontext-memory/src/test/java/io/agentscope/core/memory/autocontext/AutoContextMemoryTest.java	Updates existing assertions and adds a dedicated test to verify ReAct tool structure is preserved under Strategy 6.

[codecov]

Codecov Report

❌ Patch coverage is 88.40580% with 8 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
...ope/core/memory/autocontext/AutoContextMemory.java	88.40%	2 Missing and 6 partials ⚠️

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[LearningGp]

@shiyiyue1102 PTAL