Automations: add Archive action to hover actions of an automation history entry

### Description

Each run listed in the Automations history (`AutomationHistorySection` in `src/vs/sessions/contrib/sessions/browser/views/automationsView.ts`) shows a hover toolbar (`Menus.AutomationsHistoryItem`) with **Stop** and **Delete** actions, registered in `registerAutomationHistoryItemActions()`:

```ts
function registerAutomationHistoryItemActions(): IDisposable {
return combinedDisposable(
MenuRegistry.appendMenuItem(Menus.AutomationsHistoryItem, {
command: { id: STOP_AUTOMATION_RUN_SESSION_COMMAND_ID, title: "Stop", icon: Codicon.stopCircle },
...
}),
MenuRegistry.appendMenuItem(Menus.AutomationsHistoryItem, {
command: { id: DELETE_AUTOMATION_RUN_SESSION_COMMAND_ID, title: "Delete", icon: Codicon.trash },
...
}),
);
}
```

There is no way to archive the session behind a history entry directly from the list. Today the only way to archive a session is to open it and use the archive control in the session's own header, there's no quick action from the history row itself.

### Suggested fix

Add an **Archive** action (calling `sessionsManagementService.archiveSession(session)`, mirroring the existing Stop/Delete handling in `handleSessionToolbarAction`) to the `Menus.AutomationsHistoryItem` hover toolbar, gated by an appropriate `when` clause (e.g. not already archived, session created) similar to the existing `SessionIsArchivedContext` usage in `sessionsActions.ts`.

### Context

Raised internally:
> rob: How do automation sessions get archived, to clean up the worktree? Seems like they can only be deleted
> Ben Villalobos: currently you can only delete from the view directly. A quick way to do it would be to click into the session itself and click archive from the controls at the top