test(license): poll the one-check-at-a-time tests in a fixed order

The three tests of #373 run two branches with tokio::join! and rely on
the first branch being polled first: the check that starts first, or the
check that waits for a held turn before the time moves. tokio's join!
already starts with the first branch on its first poll, but rotates on
the next ones; `biased;` keeps the declared order on every poll and says
so in the code. The three mutations (no turn, time read before the turn,
guard dropped at once) were run again: same red tests.

Resolves #373

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src-tauri/src/commands/license_commands.rs

@@ -2624,7 +2624,9 @@ mod tests {
     // === One check at a time (#373) ===========================================================
     //
     // Each test has its own turn, standing for `REVOCATION_CHECK_TURN`: tests run on parallel
-    // threads, and a turn shared between them would decide which check goes first.
+    // threads, and a turn shared between them would decide which check goes first. `join!` is
+    // `biased`: its first branch is polled first, every time, so it is the check that starts
+    // first.
 
     /// A turn of its own for one test.
     fn new_turn() -> tauri::async_runtime::Mutex<()> {
@@ -2649,6 +2651,7 @@ mod tests {
         let turn = new_turn();
 
         let (first, second) = tokio::join!(
+            biased;
             check_revocation_in_turn(&turn, &dir.0, &url, &dec, || NOW),
             check_revocation_in_turn(&turn, &dir.0, &url, &dec, || NOW),
         );
@@ -2694,6 +2697,7 @@ mod tests {
         let turn = new_turn();
 
         let (first, second) = tokio::join!(
+            biased;
             check_revocation_in_turn(&turn, &dir.0, &url, &dec, || NOW),
             async {
                 store_license_in(&dir.0, &new_key, &dec).unwrap();
@@ -2735,6 +2739,7 @@ mod tests {
         let running = turn.lock().await;
         let (dir_ref, clock_ref, key_ref) = (&dir, &clock, &key);
         let (result, ()) = tokio::join!(
+            biased;
             check_revocation_in_turn(&turn, &dir.0, &url, &dec, || {
                 clock.load(std::sync::atomic::Ordering::SeqCst)
             }),