windows: Add support for fetching shell environment in remote projects (#39831)

Closes #39216

Note that this affects all platforms, I'm just using the prefix to make
auto-cherry-picking easier.

Release Notes:

- Fixed shell commands run by agents failing to find installed programs
in some cases.

crates/task/src/task.rs

@@ -9,6 +9,7 @@ mod task_template;
 mod vscode_debug_format;
 mod vscode_format;
 
+use anyhow::Context as _;
 use collections::{HashMap, HashSet, hash_map};
 use gpui::SharedString;
 use schemars::JsonSchema;
@@ -361,6 +362,38 @@ impl Shell {
             Shell::System => ShellKind::system(),
         }
     }
+
+    pub fn from_proto(proto: proto::Shell) -> anyhow::Result<Self> {
+        let shell_type = proto.shell_type.context("invalid shell type")?;
+        let shell = match shell_type {
+            proto::shell::ShellType::System(_) => Self::System,
+            proto::shell::ShellType::Program(program) => Self::Program(program),
+            proto::shell::ShellType::WithArguments(program) => Self::WithArguments {
+                program: program.program,
+                args: program.args,
+                title_override: None,
+            },
+        };
+        Ok(shell)
+    }
+
+    pub fn to_proto(self) -> proto::Shell {
+        let shell_type = match self {
+            Shell::System => proto::shell::ShellType::System(proto::System {}),
+            Shell::Program(program) => proto::shell::ShellType::Program(program),
+            Shell::WithArguments {
+                program,
+                args,
+                title_override: _,
+            } => proto::shell::ShellType::WithArguments(proto::shell::WithArguments {
+                program,
+                args,
+            }),
+        };
+        proto::Shell {
+            shell_type: Some(shell_type),
+        }
+    }
 }
 
 type VsCodeEnvVariable = String;