fix: Skip auto-updating .NET installs whose architecture doesn't match the current machine

[Copilot]

On an x64 machine with arm64 install records in extension state (e.g. from a prior arm64 VS Code session or settings migration), the auto-updater would download arm64 .NET and then fail to validate it — producing "the file is valid but intended for a different computer" (shown above).

Root cause

LocalInstallUpdateService.getInstallGroups() grouped all stored install records for update with no architecture guard. If state contained 9.0.16~arm64, the updater downloaded arm64 .NET and attempted to execute it for validation on the x64 process.

Changes

• LocalInstallUpdateService.ts — In getInstallGroups(), resolve currentArchitecture once via DotnetCoreAcquisitionWorker.defaultArchitecture() and continue past any install record whose architecture differs. Emits SkippingIncompatibleArchitectureInstall for each skipped install.

// Skip installs for architectures that do not match the current machine.
if (architecture !== currentArchitecture)
{
    this.eventStream.post(new SkippingIncompatibleArchitectureInstall(
        `Skipping auto-update for ${install.dotnetInstall.installId}: install architecture '${architecture}' does not match the current machine architecture '${currentArchitecture}'.`));
    continue;
}

• EventStreamEvents.ts — Added SkippingIncompatibleArchitectureInstall event class.

• LocalInstallUpdateService.test.ts — Replaced hardcoded 'x64' in all createInstallRecord calls with DotnetCoreAcquisitionWorker.defaultArchitecture() (correctness on arm64 CI runners). Replaced the "separate architecture groups" test with "It skips installs with architectures incompatible with the current machine" which asserts only the compatible-arch group is acquired/uninstalled and the skip event is emitted.