feat(tui): Set TURBO_IS_TUI environment variable when using TUI.

Author: anthonyshew

crates/turborepo-lib/src/task_graph/visitor.rs

@@ -914,6 +914,11 @@ impl ExecContext {
         cmd.env("TURBO_HASH", &self.task_hash);
         // enable task access tracing
 
+        // Allow downstream tools to detect if the task is being ran with TUI
+        if self.experimental_ui {
+            cmd.env("TURBO_IS_TUI", "true");
+        }
+
         // set the trace file env var - frameworks that support this can use it to
         // write out a trace file that we will use to automatically cache the task
         if self.task_access.is_enabled() {