Pseudoterminal guard

[edvilme]

This pull request introduces a new utility function to consistently determine when terminal activation should be skipped, and refactors related logic throughout the codebase to use this function. The main goal is to improve reliability and maintainability by centralizing the logic for skipping activation of certain terminals (such as hidden or PTY-based extension terminals).

Terminal activation skip logic improvements:

• Added a new function shouldSkipTerminalActivation in src/features/terminal/utils.ts to centralize the logic for skipping activation for terminals that are hidden from the user or are PTY-based extension terminals.
• Refactored TerminalManagerImpl in src/features/terminal/terminalManager.ts to use shouldSkipTerminalActivation instead of directly checking terminal options in multiple places, ensuring consistent behavior when opening or activating terminals. [1] [2] [3] [4]
• Updated TerminalActivationImpl in src/features/terminal/terminalActivationState.ts to use the new skip logic, preventing activation for terminals that meet the skip criteria. [1] [2]

Other changes:

• Cleaned up imports in src/features/terminal/terminalManager.ts and src/features/terminal/utils.ts to remove unused TerminalOptions and add ExtensionTerminalOptions where needed. [1] [2]

Fixes #1482