修复 max_turn_exceeded 中断提示与错误透传

[Yumiue]

Summary

• 将 Runtime max-turn 受控停止映射为 Gateway 稳定错误码 max_turn_exceeded
• 让异步 gateway.run 失败事件透传 stop_reason=max_turn_exceeded
• Web 端补齐 run_error 处理，显示明确的最大轮数提示并收敛生成状态
• 更新 Gateway 错误字典文档

Test

• go test ./internal/gateway ./internal/runtime
• go test ./internal/gateway/...
• go test ./internal/cli -run TestGatewayRuntimePortBridgeRuntimeMethods
• cd web && npm test -- eventBridge

Notes

• go test ./internal/cli 整包仍受本地 Windows 环境限制影响，失败点与本次改动无关。

close #695

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[codecov]

Codecov Report

❌ Patch coverage is 72.09302% with 12 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
internal/cli/gateway_runtime_bridge.go	0.00%	5 Missing and 1 partial ⚠️
internal/gateway/runtime_errors.go	75.00%	4 Missing ⚠️
internal/gateway/bootstrap.go	88.23%	1 Missing and 1 partial ⚠️

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[fennoai]

Review complete. I found one session/run isolation issue in the web event bridge.

[fennoai]

RunError is run-scoped, but adding it to SESSION_AGNOSTIC_EVENTS lets failures from a stale/different session bypass the session guard. The handler below then calls resetGeneratingState() and finalizeRunningToolCalls("error") globally, so if the user has switched sessions or started another run, an old run_error can stop/corrupt the current UI state. Consider only allowing mismatched RunError through when its run_id matches currentRunId, or otherwise keep the session guard and route the error to the owning session/run.