Implement Windows console with P/Invoke (VT100 + event-driven input)

[Aaronontheweb]

Parent: #77

Summary

Implement WindowsConsole using Windows Console API via P/Invoke for proper VT100 support and event-driven input.

Files to Create

• src/Termina/Platform/WindowsConsole.cs

P/Invoke Requirements

Console Mode Flags

const uint ENABLE_VIRTUAL_TERMINAL_PROCESSING = 0x0004;
const uint ENABLE_WINDOW_INPUT = 0x0008;
const uint ENABLE_MOUSE_INPUT = 0x0010;  // Optional

Required APIs

• GetStdHandle(STD_INPUT_HANDLE, STD_OUTPUT_HANDLE)
• GetConsoleMode() / SetConsoleMode()
• ReadConsoleInputW() - Read INPUT_RECORD structs
• WaitForSingleObjectEx() - Cancellable wait on input handle
• GetConsoleScreenBufferInfo() - Terminal dimensions

Input Records

[StructLayout(LayoutKind.Explicit)]
struct INPUT_RECORD
{
    [FieldOffset(0)] public ushort EventType;
    [FieldOffset(4)] public KEY_EVENT_RECORD KeyEvent;
    [FieldOffset(4)] public WINDOW_BUFFER_SIZE_RECORD WindowBufferSizeEvent;
}

Key Behaviors

1. Initialize(): Enable VT100 processing + window input events
2. ReadInputAsync(): Use WaitForSingleObjectEx with timeout for cancellation, then ReadConsoleInputW
3. Restore(): Reset console mode to original state
4. Resized: Emit when WINDOW_BUFFER_SIZE_EVENT received

Acceptance Criteria

• VT100 sequences processed correctly (borders render properly)
• Event-driven input (no polling)
• Cancellable via CancellationToken
• Window resize events detected
• Console state properly restored on dispose
• Works on Windows Terminal
• Best-effort support for Cmder/ConEmu

[Aaronontheweb]

Resolved by PR #90 - Windows console with P/Invoke implementation complete.