Fix Toast timing and alert once per shown Toast

- ToastQueue compared times unsigned: a Toast stamped a few ms after the
  main loop read the clock looked expired, so Toasts were skipped or
  shown late and bursts chained wrongly
- Notifier now beeps and flashes when each Toast appears instead of when
  the Notification arrives, so a burst alerts once per Toast

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EhqxQ49eCju4CzKYNjZzwT

test/test_toast_queue/test_toast_queue.cpp

@@ -1,5 +1,7 @@
 #include <unity.h>
 
+#include <string>
+
 #include "toast_queue.h"
 
 using namespace roro;
@@ -64,6 +66,32 @@ void test_reports_when_a_new_toast_appears() {
     TEST_ASSERT_TRUE(q.takeChanged());
 }
 
+void test_asking_with_a_slightly_older_time_does_not_expire_the_toast() {
+    // The main loop reads the time once, then a Notification pushed later in the same pass is
+    // stamped a few ms after it.
+    ToastQueue q(3000);
+    q.push("late", NotificationLevel::Info, 1005);
+    TEST_ASSERT_NOT_NULL(q.current(1000));
+    TEST_ASSERT_EQUAL_STRING("late", q.current(1000)->text.c_str());
+}
+
+void test_burst_shows_each_toast_in_turn() {
+    ToastQueue q(3000);
+    for (int i = 1; i <= 3; i++) q.push(std::to_string(i), NotificationLevel::Info, 1002);
+    TEST_ASSERT_EQUAL_STRING("1", q.current(1000)->text.c_str());
+    TEST_ASSERT_EQUAL_STRING("2", q.current(4002)->text.c_str());
+    TEST_ASSERT_EQUAL_STRING("3", q.current(7002)->text.c_str());
+    TEST_ASSERT_NULL(q.current(10002));
+}
+
+void test_each_toast_has_its_own_id() {
+    ToastQueue q(3000);
+    q.push("a", NotificationLevel::Info, 0);
+    q.push("a", NotificationLevel::Info, 0);  // same text, still a different Toast
+    uint32_t first = q.current(0)->id;
+    TEST_ASSERT_NOT_EQUAL(first, q.current(3000)->id);
+}
+
 int main() {
     UNITY_BEGIN();
     RUN_TEST(test_nothing_shown_when_empty);
@@ -73,5 +101,8 @@ int main() {
     RUN_TEST(test_flood_keeps_the_visible_toast_and_drops_the_oldest_waiting);
     RUN_TEST(test_dismiss_shows_the_next_one_immediately);
     RUN_TEST(test_reports_when_a_new_toast_appears);
+    RUN_TEST(test_asking_with_a_slightly_older_time_does_not_expire_the_toast);
+    RUN_TEST(test_burst_shows_each_toast_in_turn);
+    RUN_TEST(test_each_toast_has_its_own_id);
     return UNITY_END();
 }