Title: Feature request: Start Extension Terminal as hidden/background terminal to avoid stealing focus on VS Code

Prerequisites

• I have written a descriptive issue title.
• I have searched all issues to ensure it has not already been reported.

Summary

When VS Code starts, the PowerShell Extension Terminal launches and grabs window/panel focus,
interrupting whatever the user was doing (e.g., opening a file, using the editor).

Expected behavior

The Extension Terminal should start as a hidden background terminal. It should only become
visible/focused when the user explicitly opens it or runs a PowerShell command.

VS Code supports creating terminals in a hidden state via the hideFromUser option in the
terminal API — the extension could leverage this so IntelliSense/language services start
without the terminal panel stealing focus.

Current behavior

On VS Code startup with a .ps1 file open, the Extension Terminal panel opens and takes focus.

Steps to reproduce

1. Open VS Code with any PowerShell file
2. The Extension Terminal panel activates and steals focus from the editor

The relevant prior issues are PowerShell/vscode-powershell#1058 (F5 steals focus, partially resolved via powershell.integratedConsole.focusConsoleOnExecute: false)

Proposed Design

VSCode now supports hidden terminals please use it

Start by locating the extension terminal creation and startup activation path, then review how VS Code's terminal API handles the proposed hideFromUser option. Verify the behavior by opening VS Code with a PowerShell file and confirming the terminal remains hidden until explicitly opened or used, without stealing editor focus.