fix(autocontext): preserve tool pairs in current round compression

[Alexxigang]

Summary

• preserve tool_use and tool_result structure when Strategy 6 compresses the current round
• aggregate current-round tool calls/results into a compact assistant/tool pair instead of flattening them into a single assistant text message
• add regression coverage for current-round compression with tool interactions

Why this fix

mergeAndCompressCurrentRoundMessages() currently offloads the whole current-round segment and rewrites it as a single plain ASSISTANT text message. When that segment contains ReAct-style tool_use / tool_result exchanges, the structural pairing is lost, so the next turn can behave as if the tool call never happened and repeat the invocation.

This change keeps Strategy 6 compact, but preserves the semantic tool-call record by retaining aggregated ToolUseBlock and ToolResultBlock content in the compressed messages.

Validation

• mvn -pl agentscope-extensions/agentscope-extensions-autocontext-memory -am '-Dtest=AutoContextMemoryTest' test
• mvn -pl agentscope-extensions/agentscope-extensions-autocontext-memory -am '-Dtest=AutoContextMemoryTest,AutoContextHookTest' test

Closes #1026

[codecov]

Codecov Report

❌ Patch coverage is 84.93151% with 11 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
...ope/core/memory/autocontext/AutoContextMemory.java	84.93%	3 Missing and 8 partials ⚠️

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