feat(desktop): mid-turn steer injection and tool-call details in history

[JesonChou]

Fix two core desktop features:

1. Model dialogue mid-turn steer: when the model is running, user input is now injected as mid-turn guidance via a steer queue instead of being silently dropped by runGuarded. A runningRef replaces the stale state.running closure in handleSend, and the steer flows through App.Steer -> Controller.Steer -> Agent.Steer into a FIFO queue consumed each iteration of the agent loop, persisted to the session so it remains visible for subsequent API calls. A Steer event confirms delivery to the frontend.

2. History tool-call details: HistoryMessage now carries ToolName, ToolArgs, ToolOutput, ToolID, and ToolTruncated fields mapped from the provider's tool-call records. The history reducer and HistoryPanel's previewMessagesToItems render tool messages as ToolCard items, so switching between saved sessions shows full tool invocation details.

Changes:

• internal/event/event.go: add Steer event kind
• internal/agent/agent.go: add steerQueue, Steer/consumeSteer/ SteerConsumed/clearSteerQueue/steerQueueLen, midTurnSteerPrefix, and steer consumption/peristence in Run loop
• internal/control/controller.go: add Steer/SteerConsumed methods
• desktop/app.go: add App.Steer, expand HistoryMessage struct with tool fields, map tool messages in historyMessages via toolCallByID
• desktop/frontend/src/lib/bridge.ts: add Steer to AppBindings and mock
• desktop/frontend/src/lib/types.ts: add steer event kind, tool fields to HistoryMessage
• desktop/frontend/src/lib/useController.ts: add steer callback, update history reducer for tool messages
• desktop/frontend/src/App.tsx: add runningRef + steer in handleSend
• desktop/frontend/src/components/HistoryPanel.tsx: update previewMessagesToItems for tool messages