Add Agent Host PowerShell nested script-block auto-approval regressions

[Anthony Kim (anthonykim1)]

Part of: #328133

• Add Agent Host PowerShell regressions for nested commands inside Measure-Command and related script-block wrappers.
• Keep an outer allow rule from hiding nested denied cmdlets such as Set-Content, Invoke-Expression, and Start-Process.
• Cover the visible-separator control path and show that selecting the Bash grammar can still make the same rules opaque.
• Add a session-permission proof that PowerShell script-block payloads with nested denials require confirmation, including when shell language is missing.

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Inspirations from:

• Nested script-block coverage starts from the existing denies commands nested inside script blocks test.
• PowerShell dialect selection comes from CommandAutoApprover language handling and the PowerShell capture query in _extractSubCommands.
• Session-level fail-closed missing dialect behavior comes from SessionPermissionManager.getAutoApproval.
• The production fix this protects is #328133.

[Copilot]

Pull request overview

Adds regression coverage for PowerShell nested script-block auto-approval behavior.

Changes:

• Tests nested denied cmdlets and incorrect Bash grammar selection.
• Verifies session permissions fail closed for nested denials and missing dialects.

Show a summary per file

File	Description
commandAutoApprover.test.ts	Adds parser-level PowerShell regressions.
sessionPermissions.test.ts	Adds session-level confirmation regressions.

Review details

• Files reviewed: 2/2 changed files
• Comments generated: 1
• Review effort level: Balanced