Expose AppInstallManager download-queue prioritization

Parent: #232

Dependencies and access restriction

Depends on #233, #234, #236. Implementation remains blocked until the supported-access gate and listed prerequisites are complete.

Microsoft documents AppInstallManager access as protected by a private capability restricted to Microsoft-developed apps. Do not bypass that restriction or treat runFullTrust/admin access alone as sufficient.

API scope

MoveToFrontOfDownloadQueue.

Acceptance criteria

• Accept exact documented product identity and correlation input, including unambiguous typed pipeline targeting.
• Require ShouldProcess before modifying queue priority; -WhatIf must not reorder downloads.
• Document the API's actual queue/user/group scope and ordering behavior rather than promising deterministic installation order.
• Preserve missing/completed-item races, access errors and native failures. Report a prioritization request, not download or install completion.
• Keep unrelated queue items untouched except the ordering effects inherent in the documented operation.

Shared delivery requirements

Follow the parent epic's compiled-C# contract, user-scope and capability/version gates. Include deterministic Pester 6.2+ coverage, comment-based help, public documentation and unreleased notes in the same implementation PR. Use fail-closed fake adapters for side effects; no real installs, entitlement grants or settings changes in CI. Preserve original errors and distinguish unavailable, unknown, requested and completed outcomes.

Documented API references

• https://learn.microsoft.com/uwp/api/windows.applicationmodel.store.preview.installcontrol.appinstallmanager.movetofrontofdownloadqueue

Start with parent issue #232 and dependencies #233, #234, and #236, then review the documented MoveToFrontOfDownloadQueue API. Use the compiled-C# contract and Pester 6.2+ coverage requirements as entry points; done means the supported-access gates are honored, ShouldProcess and -WhatIf behave correctly, and documentation, help, and unreleased notes describe requested rather than completed work.