Function session_user_and_home

crates/openshell-supervisor-process/src/ssh.rs:670–689

Derive the session USER and HOME from the policy's `run_as_user`. For name-based identities, looks up the home directory via `/etc/passwd` (or defaults to `/home/{user}`). For numeric UIDs, there is no passwd entry — falls back to `("{uid}", "/sandbox")` so the agent session still has a meaningful USER identifier.

(policy: &SandboxPolicy)

/// `("{uid}", "/sandbox")` so the agent session still has a meaningful
/// USER identifier.
fn session_user_and_home(policy: &SandboxPolicy) -> (String, String) {
    match policy.process.run_as_user.as_deref() {
        Some(user) if !user.is_empty() => {
            // Numeric UID — no passwd entry expected; use default HOME.
            if user.parse::<u32>().is_ok() {
                return (user.to_string(), "/sandbox".to_string());
            }
            // Name-based identity — look up home from /etc/passwd.
            let home = nix::unistd::User::from_name(user)
                .ok()
                .flatten()
                .map_or_else(
                    || format!("/home/{user}"),
                    |u| u.dir.to_string_lossy().into_owned(),
                );
            (user.to_string(), home)
        }
        _ => ("sandbox".to_string(), "/sandbox".to_string()),
    }
}

#[allow(clippy::too_many_arguments)]
fn apply_child_env(