test(cli): serialize cli_tests via serial_test

Replace the hand-rolled `SERIAL` mutex guarding process-global env access
with serial_test's `#[serial]` attribute on each test.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/Cargo.toml b/Cargo.toml
index 544bf3a..6aeddda 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -24,6 +24,7 @@ reqwest = "0.13.4"
 serde = { version = "1.0.228", features = ["derive"] }
 serde_json = { version = "1.0.149", features = ["preserve_order"] }
 serde_urlencoded = "0.7.1"
+serial_test = "3.5.0"
 sha1 = "0.11.0"
 sha2 = "0.11.0"
 tempfile = "3.27.0"