Fix DevTools URL opening on Windows

[vaspadi]

Problem

I wasn’t able to open DevTools either via :FlutterOpenDevTools or automatically when starting a debug session.
This issue has existed for several months, but I managed by manually running DevTools with fvm dart devtools and copying the URL from the REPL.

Solution

The root cause was the use of the explorer command on Windows. explorer truncated the URL and opened an invalid path. I replaced it with start and adjusted the method so that it executes successfully without raising ENOENT: no such file or directory.

Environment

• OS: Windows 11 Home
• GNU bash: 5.2.37(1)-release (x86_64-pc-msys)
• FVM: v3.2.1
• flutter-tools.nvim: Commit 65b7399
• Neovim: v0.11.4

[sidlatau]

Thanks for the fix!