fix: Update METAR on hash change and prevent re-display of current METAR

Co-authored-by: aider (gemini/gemini-2.5-pro) <aider@aider.chat>

metar.html

@@ -76,6 +76,7 @@
 
         let currentMetarSections = [];
         let currentSectionIndex = 0;
+        let currentMetarIndex = -1;
 
         // --- METAR Ranking ---
 
@@ -832,6 +833,11 @@
                 metarIndex = Math.floor(Math.random() * Math.random() * metars.length);
             }
 
+            if (metarIndex === currentMetarIndex) {
+                return; // Already displaying this METAR
+            }
+            currentMetarIndex = metarIndex;
+
             const metarString = metars[metarIndex].metar;
             history.replaceState(null, '', '#' + metarIndex);
 
@@ -896,6 +902,13 @@
 
         newMetarBtn.addEventListener('click', () => displayMetar());
         decodeAllCheckbox.addEventListener('change', updateDisplay);
+        window.addEventListener('hashchange', () => {
+            const hash = window.location.hash.substring(1);
+            const index = parseInt(hash, 10);
+            if (!isNaN(index) && index >= 0 && index < metars.length) {
+                displayMetar(index);
+            }
+        });
 
         function updateDisplay() {
             if (currentMetarSections.length === 0) return;