Make ShellBuilder::new not branch on a remote shell (#39493)

Release Notes:

- Fixed claude code agent login on remotes

Co-authored-by: Max Brunsfeld <max@zed.dev>
Co-authored-by: Cole Miller <cole@zed.dev>

crates/assistant_tools/src/terminal_tool.rs

@@ -127,11 +127,13 @@ impl Tool for TerminalTool {
             }),
             None => Task::ready(None).shared(),
         };
-        let remote_shell = project.update(cx, |project, cx| {
-            project
-                .remote_client()
-                .and_then(|r| r.read(cx).default_system_shell())
-        });
+        let shell = project
+            .update(cx, |project, cx| {
+                project
+                    .remote_client()
+                    .and_then(|r| r.read(cx).default_system_shell())
+            })
+            .unwrap_or_else(|| get_default_system_shell());
 
         let env = cx.spawn(async move |_| {
             let mut env = env.await.unwrap_or_default();
@@ -144,12 +146,9 @@ impl Tool for TerminalTool {
         let build_cmd = {
             let input_command = input.command.clone();
             move || {
-                ShellBuilder::new(
-                    remote_shell.as_deref(),
-                    &Shell::Program(get_default_system_shell()),
-                )
-                .redirect_stdin_to_dev_null()
-                .build(Some(input_command.clone()), &[])
+                ShellBuilder::new(&Shell::Program(shell))
+                    .redirect_stdin_to_dev_null()
+                    .build(Some(input_command), &[])
             }
         };