util: Fix shell kind in windows based on program path (#39696)

Closes #39614

The `ShellKind` struct is built on Windows' side, meaning that when
connecting to remotes, we fall back to PowerShell construction, even if
the shell program we are spawning is a unix program.

This broke tasks creation since we are using the shell kind to construct
args:


https://github.com/zed-industries/zed/blob/d04ac864b8cb78ee888ce03323e34c17a6dd16b9/crates/project/src/terminals.rs#L149

In normal terminals this only affected activation scripts (only place
where shell kind is used)

I don't have a Windows machine to test it, so I would appreciate any
help with testing!

Release Notes:

- Fixed an issue where tasks could not be executed in Windows WSL

---------

Signed-off-by: Marco Mihai Condrache <52580954+marcocondrache@users.noreply.github.com>

crates/util/src/shell.rs

@@ -173,18 +173,16 @@ impl fmt::Display for ShellKind {
 
 impl ShellKind {
     pub fn system() -> Self {
-        Self::new(&get_system_shell())
+        Self::new(&get_system_shell(), cfg!(windows))
     }
 
-    pub fn new(program: impl AsRef<Path>) -> Self {
+    pub fn new(program: impl AsRef<Path>, is_windows: bool) -> Self {
         let program = program.as_ref();
-        let Some(program) = program.file_stem().and_then(|s| s.to_str()) else {
-            return if cfg!(windows) {
-                ShellKind::PowerShell
-            } else {
-                ShellKind::Posix
-            };
-        };
+        let program = program
+            .file_stem()
+            .unwrap_or_else(|| program.as_os_str())
+            .to_string_lossy();
+
         if program == "powershell" || program == "pwsh" {
             ShellKind::PowerShell
         } else if program == "cmd" {
@@ -204,7 +202,7 @@ impl ShellKind {
         } else if program == "sh" || program == "bash" {
             ShellKind::Posix
         } else {
-            if cfg!(windows) {
+            if is_windows {
                 ShellKind::PowerShell
             } else {
                 // Some other shell detected, the user might install and use a