fix(terminal): allow shell integration in powershell audit mode

[RITHIK KUMARAN K (RITHIKKUMARAN)]

Fixes #283151

Description

This PR allows VS Code's Terminal Shell Integration to initialize correctly when PowerShell 7.4+ is operating in the new ConstrainedLanguage Audit mode.

Root Cause:
PowerShell 7.4 introduced a security audit mode. When a system (such as modern Windows 11 machines) has a Windows Defender Application Control (WDAC) audit-only policy active, PowerShell reports its $ExecutionContext.SessionState.LanguageMode as ConstrainedLanguage. However, it functions with full, unrestricted semantics because it is only logging actions, not blocking them. The shellIntegration.ps1 script historically bailed out immediately if the language mode was not FullLanguage, incorrectly breaking terminal features (prompt tracking, command decorations) for these users.

Proposed Changes:

• Updated the language mode guard in shellIntegration.ps1 to query [System.Management.Automation.Security.SystemPolicy]::GetSystemLockdownPolicy() when a restricted language mode is detected.
• If the lockdown policy explicitly returns Audit, we safely bypass the bailout and allow shell integration to initialize.
• Included a try...catch wrapper to ensure this check safely fails open on older PowerShell versions that do not support this API.
• Replicated the logic in the Copilot simulation test fixture to ensure consistency.

How to test

1. On a Windows 11 machine, enable a WDAC / App Control audit-only policy.
2. Launch PowerShell 7.4+. Verify that $ExecutionContext.SessionState.LanguageMode reports ConstrainedLanguage and [System.Management.Automation.Security.SystemPolicy]::GetSystemLockdownPolicy() reports Audit.
3. Open the integrated terminal in VS Code using the pwsh profile.
4. Verify that terminal shell integration (prompt tracking and command boundaries) successfully initializes instead of silently aborting.

[Copilot]

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[vs-code-engineering]

📬 CODENOTIFY

The following users are being notified based on files changed in this PR:

Anthony Kim (@anthonykim1)

Matched files:

• src/vs/workbench/contrib/terminal/common/scripts/shellIntegration.ps1