[5/6] Show tool call durations / 展示工具调用耗时

[SivanCola]

Summary / 摘要

• Track tool call start and completion timing in the local wire/session model.
• Surface elapsed milliseconds in tool process-card headers when available.
• Preserve existing tool-call rendering when duration data is absent.

Validation / 验证

• npm run typecheck && npm run build
• go test . -run 'TestPreviewSessionMessages|TestHistoryMessages|TestToWireTool' (desktop)\n- go test ./internal/event ./internal/serve ./internal/agent ./internal/control\n- git diff --check

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Render the emitted duration in the frontend

When a tool result includes this new durationMs field, the desktop frontend still drops it: WireTool/Item have no durationMs, the tool_result reducer never copies it, and ToolCard only renders the status glyph (I checked desktop/frontend/src and there are no durationMs references). As a result the backend now emits timing data, but desktop users still won't see tool call durations for any completed tool call.

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