fix(deps): extend libc to all Unix targets for FreeBSD compatibility (#1173)

`libc` was declared only for macOS and Linux, causing a build failure on
FreeBSD (#1143). All call sites that use `libc` are already guarded with
`#[cfg(unix)]` or narrower OS-specific guards, so broadening the
dependency to `cfg(unix)` fixes FreeBSD (and other BSDs) with no
behavioural change on macOS or Linux.

Co-authored-by: Vince <liuwenchang.x@qq.com>

crates/tui/Cargo.toml

@@ -75,10 +75,7 @@ wiremock = "0.6"
 pretty_assertions = "1.4"
 vt100 = "0.15"
 
-[target.'cfg(target_os = "macos")'.dependencies]
-libc = "0.2"
-
-[target.'cfg(target_os = "linux")'.dependencies]
+[target.'cfg(unix)'.dependencies]
 libc = "0.2"
 
 [target.'cfg(target_os = "windows")'.dependencies]