fix(installer): reject user-writable SMBus broker paths

[hyperb1iss]

Motivation

• Prevent a local privilege-escalation vector where the SMBus broker service can be registered with a BinaryPathName that points into a user-writable (current-user) install tree, which would allow a low-privileged user to replace the broker binary and gain SYSTEM execution.

Description

• Add Assert-ServiceBrokerPath to scripts/install-windows-smbus-service.ps1 (mirroring the existing PawnIO guard) and call it immediately after Resolve-SmbusBroker to reject broker executables located under %LOCALAPPDATA%, %APPDATA%, %USERPROFILE%, or C:\Users\* before creating the New-Service entry.

Testing

• Attempted to run a PowerShell presence check with pwsh -NoLogo -NoProfile -Command "Get-Command pwsh | Out-Null", but pwsh is not installed in this Linux container so runtime script execution tests could not be performed; the change is minimal and follows the script's existing path-hardening pattern.

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Codex Task

[coderabbitai]

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ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 650867f7-fd67-4c9a-89c6-4f265320ab0d

📥 Commits

Reviewing files that changed from the base of the PR and between 6f749b6 and 7e3133e.

📒 Files selected for processing (1)

• scripts/install-windows-smbus-service.ps1

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch codex/propose-fix-for-local-privilege-escalation-vulnerability

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