Changed sked opportunity highlighting mechanism to more precision, updated the manual

src/main/java/kst4contest/model/ChatMemberDirectionOpportunityTest.java

@@ -0,0 +1,34 @@
+package kst4contest.model;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+class ChatMemberDirectionOpportunityTest {
+
+    @Test
+    void directionalOpportunityExpiresAfterConfiguredValidityPeriod() {
+        ChatMember member = new ChatMember();
+
+        member.setInAngleAndRange(true);
+        long afterActivationEpochMs = System.currentTimeMillis();
+
+        assertTrue(member.isInAngleAndRangeAt(afterActivationEpochMs));
+        assertFalse(member.isInAngleAndRangeAt(
+                afterActivationEpochMs
+                        + ChatMember.DIRECTION_OPPORTUNITY_VALIDITY_MILLIS
+                        + 1L));
+    }
+
+    @Test
+    void directionalOpportunityCanBeClearedImmediately() {
+        ChatMember member = new ChatMember();
+
+        member.setInAngleAndRange(true);
+        assertTrue(member.isInAngleAndRange());
+
+        member.setInAngleAndRange(false);
+        assertFalse(member.isInAngleAndRange());
+    }
+}