fix(tool): scope internal emitter callbacks to agent calls

[CryoThrust]

Summary\n\nFixes #3065.\n\nThe framework-internal ToolEmitter callback was stored as mutable state on a shared Toolkit/ToolExecutor. Concurrent ReActAgent calls could therefore route progress from one tool invocation to another request.\n\nThis draft keeps the existing public ToolEmitter API and carries the internal callback through the call-scoped ToolCallParam:\n\n- ReActAgent creates one callback per event stream.\n- Toolkit/ToolExecutor pass it through each tool execution.\n- DefaultToolEmitter captures the callback when the invocation starts.\n- The legacy setInternalChunkCallback path remains available for compatibility.\n\n## Regression coverage\n\nAdded a deterministic barrier-based test with two concurrent calls sharing one Toolkit. Each callback receives only its own tool ID and progress payload.\n\nVerification:\n\n- [INFO] Scanning for projects...

[ERROR] [ERROR] Could not find the selected project in the reactor: agentscope-core @
[ERROR] Could not find the selected project in the reactor: agentscope-core -> [Help 1]
[ERROR]
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR]
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/MavenExecutionException\n- [INFO] Scanning for projects...
[ERROR] [ERROR] Could not find the selected project in the reactor: agentscope-core @
[ERROR] Could not find the selected project in the reactor: agentscope-core -> [Help 1]
[ERROR]
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR]
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/MavenExecutionException\n- 28 existing ToolCallParam/ToolEmitter tests plus the new concurrency case pass.\n\nThis is a draft because the five-argument Toolkit.callTools overload is an internal API shape for maintainer review. I can adapt it to another internal execution-context mechanism if preferred.

[CryoThrust]

Rebased the draft onto the latest upstream main (d20ebbe0) and removed unrelated historical commits from the PR branch. The head is now mergeable. Re-ran Spotless and the focused core tests on the rebased head: 29 tests passed (0 failures, 0 errors). The implementation remains intentionally draft until maintainers confirm the preferred internal execution-context API.

[codecov]

Codecov Report

❌ Patch coverage is 73.07692% with 14 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
...e/src/main/java/io/agentscope/core/ReActAgent.java	67.64%	8 Missing and 3 partials ⚠️
...ain/java/io/agentscope/core/tool/ToolExecutor.java	72.72%	2 Missing and 1 partial ⚠️

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