Add native Windows support (#91)

- Native Windows daemon using TCP loopback endpoints
- Direct-mode fallback for CLI/daemon compatibility
- Comment operations over RPC
- PowerShell installer script
- Go 1.24 requirement
- Cross-OS testing documented

Co-authored-by: danshapiro <danshapiro@users.noreply.github.com>
Amp-Thread-ID: https://ampcode.com/threads/T-c6230265-055f-4af1-9712-4481061886db
Co-authored-by: Amp <amp@ampcode.com>

internal/rpc/transport_windows.go

@@ -0,0 +1,69 @@
+//go:build windows
+
+package rpc
+
+import (
+	"encoding/json"
+	"errors"
+	"net"
+	"os"
+	"time"
+)
+
+type endpointInfo struct {
+	Network string `json:"network"`
+	Address string `json:"address"`
+}
+
+func listenRPC(socketPath string) (net.Listener, error) {
+	listener, err := net.Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		return nil, err
+	}
+
+	info := endpointInfo{
+		Network: "tcp",
+		Address: listener.Addr().String(),
+	}
+
+	data, err := json.Marshal(info)
+	if err != nil {
+		listener.Close()
+		return nil, err
+	}
+
+	if err := os.WriteFile(socketPath, data, 0o600); err != nil {
+		listener.Close()
+		return nil, err
+	}
+
+	return listener, nil
+}
+
+func dialRPC(socketPath string, timeout time.Duration) (net.Conn, error) {
+	data, err := os.ReadFile(socketPath)
+	if err != nil {
+		return nil, err
+	}
+
+	var info endpointInfo
+	if err := json.Unmarshal(data, &info); err != nil {
+		return nil, err
+	}
+
+	if info.Address == "" {
+		return nil, errors.New("invalid RPC endpoint: missing address")
+	}
+
+	network := info.Network
+	if network == "" {
+		network = "tcp"
+	}
+
+	return net.DialTimeout(network, info.Address, timeout)
+}
+
+func endpointExists(socketPath string) bool {
+	_, err := os.Stat(socketPath)
+	return err == nil
+}