Fix Windows upgrade command to preserve command-line arguments during elevation

[Copilot]

On Windows, vfox upgrade re-launches with admin privileges but only passed "upgrade" to the elevated process, discarding flags like --debug. Additionally, ShellExecuteW failures were silent.

Changes

Argument forwarding: Pass all os.Args[1:] to elevated process instead of just command name

Windows command-line escaping: Implement proper argument escaping per Microsoft rules:

• Quote arguments containing spaces, tabs, newlines, or quotes
• Double backslashes before quotes and at string end when quoted
• Leave simple arguments unquoted

Error handling: Check ShellExecuteW return value (must be > 32)

Implementation

// Before: only command name passed
arg, _ := syscall.UTF16PtrFromString(SelfUpgradeName)

// After: all arguments with proper escaping
quotedArgs := make([]string, 0, len(os.Args)-1)
for _, arg := range os.Args[1:] {
    quotedArgs = append(quotedArgs, escapeArg(arg))
}
args := strings.Join(quotedArgs, " ")
arg, _ := syscall.UTF16PtrFromString(args)

// Check for failure
ret, _, _ := run.Call(...)
if ret <= 32 {
    return syscall.Errno(ret)
}

The escapeArg() function handles edge cases like path with space\\ → "path with space\\\\" and --flag="value" → "--flag=\"value\"".

Original prompt

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This section details on the original issue you should resolve

<issue_title>[BUG]: vfox upgrade not work</issue_title>
<issue_description>Version
v0.9.2
OS
Windows

Describe the bug
vfox upgrade didn't work; it only outputs the current version and the latest available. Otherwise, I added the --debug for showing debug information, but it didn't work either.

Screenshots[optional]

</issue_description>

<agent_instructions>Please check for any issues.</agent_instructions>

Comments on the Issue (you are @copilot in this section)

• Fixes [BUG]: vfox upgrade not work #604

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