FRE dead-ends when PowerShell execution policy blocks shell integration

Steps to reproduce

1. Set the PowerShell execution policy to Restricted or AllSigned.
2. Launch Intelligent Terminal for the first time.
3. In the FRE, enable automatic error detection and click Save.

Expected Behavior

The FRE either installs shell integration in a way that works under a restrictive policy, or offers a one-click way to relax the policy, then re-probes and continues without the user leaving the app.

Actual Behavior

Shell integration fails. The FRE dead-ends on a red banner with a "Learn how to fix this manually" link in the bottom left. The user has to leave the app, read docs, run a command in another window, and come back.

Proposed fix

Either of:

• Paste the integration block inline into the profile. PowerToys works around this same restriction that way.
• Replace the manual link with an "Enable now" button that runs Set-ExecutionPolicy -Scope CurrentUser RemoteSigned (no elevation required), re-probes shell integration, and turns error detection back on.

Keep the manual path as a fallback for GPO-locked machines, where the policy cannot be changed per-user.

Related: #328 (closed, GPO-locked variant), #129 (closed, ACP transport error when shell integration can't initialize), #127 (closed, OneDrive-related shell integration failure).