fix(agui): stop emitting RUN_FINISHED after RUN_ERROR by default (#2646)

## Summary
- Treat `RUN_ERROR` as the terminal event by default, matching AG-UI
lifecycle semantics (`RUN_ERROR` and `RUN_FINISHED` are mutually
exclusive).
- Add `emitRunFinishedAfterError` (default `false`) so legacy clients
can still opt into the previous `RUN_ERROR` + `RUN_FINISHED` behavior.
- Wire the flag through adapter/processor/resume error paths and Spring
Boot `agentscope.agui.emit-run-finished-after-error`.

Fixes https://github.com/agentscope-ai/agentscope-java/issues/2642

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Co-authored-by: jujn <2087687391@qq.com>