feat: add plan mode frontend support with mode toggle and plan review UI

- Add InteractionMode type and ExitPlanModeRequestedEvent to sidecar contracts
- Add PendingPlanReviewRecord domain type and interactionMode to SessionRecord
- Wire onExitPlanMode callback through SidecarClient and RunTurnPendingCommand
- Pass session interaction mode to RunTurnCommand for sidecar consumption
- Handle exit-plan-mode-requested events in AryxAppService
- Add setSessionInteractionMode and dismissSessionPlanReview IPC methods
- Create PlanReviewBanner component with summary, markdown content, and actions
- Add plan mode toggle pill in ChatPane composer area
- Wire implement action as follow-up message (graceful degradation)
- Clear pending plan review on new turn, turn completion, and cancellation

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

src/preload/index.ts

@@ -37,6 +37,8 @@ const api: ElectronApi = {
   cancelSessionTurn: (input) => ipcRenderer.invoke(ipcChannels.cancelSessionTurn, input),
   resolveSessionApproval: (input) => ipcRenderer.invoke(ipcChannels.resolveSessionApproval, input),
   resolveSessionUserInput: (input) => ipcRenderer.invoke(ipcChannels.resolveSessionUserInput, input),
+  setSessionInteractionMode: (input) => ipcRenderer.invoke(ipcChannels.setSessionInteractionMode, input),
+  dismissSessionPlanReview: (input) => ipcRenderer.invoke(ipcChannels.dismissSessionPlanReview, input),
   updateSessionModelConfig: (input) =>
     ipcRenderer.invoke(ipcChannels.updateSessionModelConfig, input),
   querySessions: (input) => ipcRenderer.invoke(ipcChannels.querySessions, input),