Complete milestone 09 world integration gate (#75)

tests/compat/build.rs

@@ -1,6 +1,7 @@
 use std::path::Path;
 
 const KEYS: [&str; 3] = ["GRID_USER", "GRID_PASSWORD", "GRID_LOGIN_URL"];
+const LIVE_OPT_IN: &str = "RUN_LIVE_TESTS";
 
 fn dotenv_has(path: &Path, key: &str) -> bool {
     std::fs::read_to_string(path).is_ok_and(|contents| {
@@ -22,9 +23,19 @@ fn main() {
     for key in KEYS {
         println!("cargo:rerun-if-env-changed={key}");
     }
-    if KEYS.iter().all(|key| {
-        std::env::var(key).is_ok_and(|value| !value.trim().is_empty()) || dotenv_has(&dotenv, key)
-    }) {
+    println!("cargo:rerun-if-env-changed={LIVE_OPT_IN}");
+    let opted_in = std::env::var(LIVE_OPT_IN).is_ok_and(|value| {
+        matches!(
+            value.trim().to_ascii_lowercase().as_str(),
+            "1" | "true" | "yes"
+        )
+    });
+    if opted_in
+        && KEYS.iter().all(|key| {
+            std::env::var(key).is_ok_and(|value| !value.trim().is_empty())
+                || dotenv_has(&dotenv, key)
+        })
+    {
         println!("cargo:rustc-cfg=live_grid_credentials");
     }
 }