Complete Windows platform support gaps across runtime

[KrisSimon]

Problem

Windows support has significant gaps across multiple subsystems. 74 #if os(Windows) blocks exist but many are incomplete or missing fallbacks.

Gap 1: Plugin loading uses dlopen (POSIX-only)

Files: NativePluginHost.swift:251, PluginLoader.swift:303

dlopen/dlsym/dlerror are called on non-Windows platforms, but the Windows LoadLibraryW/GetProcAddress path has issues:

• Library search uses lib prefix (Unix convention) — Windows DLLs don't use lib prefix
• Hardcoded forward slashes in target/release/lib{name}.{ext} paths
• No FormatMessage equivalent for Windows error reporting (vs dlerror)

Gap 2: FileMonitor uses 1-second polling instead of ReadDirectoryChangesW

File: Windows/WindowsFileMonitor.swift

Polls directories every 1 second with O(n) scans. The correct Windows API (ReadDirectoryChangesW) is event-driven and O(1). Comment at line 6 acknowledges this.

Gap 3: HTTP response duration hardcoded to 0

File: Windows/WindowsHTTPServer.swift:185

durationMs: 0 // TODO: Track duration

All HTTP metrics show 0ms on Windows.

Gap 4: Terminal hidden input missing

File: Terminal/InputHandler.swift:87

Password input shows plaintext on Windows. Needs SetConsoleMode to disable echo.

Gap 5: Metrics collection missing

Files: MetricsCollector.swift, SystemMetricsService.swift

System metrics (CPU, memory) only implemented for macOS/Linux. No Windows GetProcessMemoryInfo/GetSystemTimes integration.

Gap 6: LLVM CodeGenerator entirely disabled

File: AROCompiler/LLVMC/LLVMCodeGenerator.swift:5

#if !os(Windows)

aro build is non-functional on Windows.

Suggested Fix

Create a platform abstraction layer:

protocol PlatformServices {
    func loadDynamicLibrary(at path: URL) throws -> DynamicLibraryHandle
    func createFileMonitor(path: URL) -> FileMonitorProtocol
    func hiddenInput(prompt: String) -> String
    func systemMetrics() -> SystemMetrics
}

Implement per-platform with compile-time selection. This eliminates scattered #if os(Windows) blocks.

---

Synced from GitLab issue #203