cmd/drover: ReElevate — surface UTF16 + Getwd errors, escape quotes

Code review found 5 silently-ignored errors in ReElevate (UTF16
conversions and os.Getwd) plus unescaped argument quoting that
breaks args containing literal `"`. Each error is now wrapped with
a clear message; quotes are backslash-escaped per the MSVC argv
convention.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

cmd/drover/uac_windows.go

@@ -3,7 +3,9 @@
 package main
 
 import (
+	"fmt"
 	"os"
+	"strings"
 	"syscall"
 	"unsafe"
 
@@ -59,15 +61,23 @@ func ReElevate(args []string) error {
 	if err != nil {
 		return err
 	}
-	verb, _ := syscall.UTF16PtrFromString("runas")
-	exePtr, _ := syscall.UTF16PtrFromString(exe)
+	verb, err := syscall.UTF16PtrFromString("runas")
+	if err != nil {
+		return fmt.Errorf("encode verb: %w", err)
+	}
+	exePtr, err := syscall.UTF16PtrFromString(exe)
+	if err != nil {
+		return fmt.Errorf("encode exe: %w", err)
+	}
 
 	var paramsPtr *uint16
 	if len(args) > 0 {
-		// Quote each arg in case of spaces.
+		// Quote each arg in case of spaces, and escape internal quotes.
 		quoted := make([]string, len(args))
 		for i, a := range args {
-			quoted[i] = `"` + a + `"`
+			// Escape any internal quotes with backslash (MSVC argv convention).
+			escaped := strings.ReplaceAll(a, "\"", "\\\"")
+			quoted[i] = `"` + escaped + `"`
 		}
 		joined := ""
 		for i, q := range quoted {
@@ -76,11 +86,20 @@ func ReElevate(args []string) error {
 			}
 			joined += q
 		}
-		paramsPtr, _ = syscall.UTF16PtrFromString(joined)
+		paramsPtr, err = syscall.UTF16PtrFromString(joined)
+		if err != nil {
+			return fmt.Errorf("encode params: %w", err)
+		}
 	}
 
-	cwd, _ := os.Getwd()
-	cwdPtr, _ := syscall.UTF16PtrFromString(cwd)
+	cwd, err := os.Getwd()
+	if err != nil {
+		return fmt.Errorf("get cwd: %w", err)
+	}
+	cwdPtr, err := syscall.UTF16PtrFromString(cwd)
+	if err != nil {
+		return fmt.Errorf("encode cwd: %w", err)
+	}
 
 	// SW_NORMAL = 1
 	return windows.ShellExecute(0, verb, exePtr, paramsPtr, cwdPtr, 1)