[UX/Windows] PowerShell swallows -- in mise exec, resulting in confusing missing <COMMAND> error

[zhangjiabo1107]

Describe the bug:
When using mise exec (or mise x) in Windows PowerShell or Windows Terminal, running a command with the -- separator fails because PowerShell intercepts and removes the -- before passing the arguments to mise.exe. This results in a confusing error for Windows users who copy-paste commands from the documentation.

Steps to reproduce:

1. Open PowerShell on Windows.
2. Run: mise x python@3.13 -- python -v
3. See the error:

error: the following required arguments were not provided:
  <COMMAND>...

Usage: mise.exe exec <TOOL@VERSION>... -- <COMMAND>...

Workaround found:
The user has to escape the double-dash specifically for PowerShell. All of the following work:

mise x python@3.14 "--" python --version
mise x python@3.14 `-- python --version

Why this happens:
This is a known quirk of PowerShell's argument parser when calling native executables. The -- token is consumed by PowerShell itself, so mise.exe's argument array (argv) literally does not contain the separator. Thus, clap correctly complains about the missing <COMMAND>.

Suggested Solutions (for Developer Experience):
Since mise cannot prevent PowerShell from modifying the arguments beforehand, I suggest we improve the UX/DX for Windows users:

1. Enhance the Error Message: When this specific missing <COMMAND> error occurs on Windows targets, append a hint. For example:
   Hint: If you are using PowerShell, it might be consuming the -- separator. Try escaping it like "--" or `--.
2. Documentation update: Add a small note in the Windows/PowerShell section of the mise documentation or the mise exec help text mentioning this behavior.
3. Make -- optional (Alternative): If possible, fallback to treating the first argument that isn't a valid <TOOL@VERSION> format as the start of the <COMMAND>. (Though I understand this might introduce parsing ambiguity).

Environment:

• OS: Windows 11
• Shell: PowerShell 7.6.1 / Windows Terminal
• mise version: 2026.5.1 windows-x64 (2026-05-05)