zlog: Replace usages of env_logger in tests with zlog (#31436)

Also fixes:
https://github.com/zed-industries/zed/pull/31400#issuecomment-2908165249

Release Notes:

- N/A *or* Added/Fixed/Improved ...

crates/assistant_tool/Cargo.toml

@@ -37,7 +37,6 @@ buffer_diff = { workspace = true, features = ["test-support"] }
 collections = { workspace = true, features = ["test-support"] }
 clock = { workspace = true, features = ["test-support"] }
 ctor.workspace = true
-env_logger.workspace = true
 gpui = { workspace = true, features = ["test-support"] }
 language = { workspace = true, features = ["test-support"] }
 language_model = { workspace = true, features = ["test-support"] }
@@ -48,3 +47,4 @@ rand.workspace = true
 settings = { workspace = true, features = ["test-support"] }
 text = { workspace = true, features = ["test-support"] }
 util = { workspace = true, features = ["test-support"] }
+zlog.workspace = true

crates/assistant_tool/src/action_log.rs

@@ -717,9 +717,7 @@ mod tests {
 
     #[ctor::ctor]
     fn init_logger() {
-        if std::env::var("RUST_LOG").is_ok() {
-            env_logger::init();
-        }
+        zlog::init_test();
     }
 
     fn init_test(cx: &mut TestAppContext) {