feat: Add support for decoding obscuration remarks like FG8

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

metar.html

@@ -208,12 +208,30 @@
             return `${code}: ${decodedParts.join(', ')}`;
         }
 
+        function decodeObscurationRemark(code) {
+            const weatherMap = {
+                'FG': 'Fog',
+                'BR': 'Mist',
+                'FU': 'Smoke',
+                'HZ': 'Haze',
+                'DU': 'Widespread dust',
+                'SA': 'Sand',
+            };
+            const weatherCode = code.substring(0, 2);
+            const oktas = code.substring(2);
+            const weatherName = weatherMap[weatherCode];
+            return `${code}: ${weatherName} obscuring ${oktas}/8 of the sky`;
+        }
+
         function decodeRemarks(parts) {
             let decoded = ["RMK: Remarks"];
             const weatherRegex = /^([+-]|VC)?(MI|PR|BC|DR|BL|SH|TS|FZ|DZ|RA|SN|SG|IC|PL|GR|GS|UP|BR|FG|FU|VA|DU|SA|HZ|PY|PO|SQ|FC|SS|DS|TR)+$/;
+            const obscurationRegex = /^(FG|BR|FU|HZ|DU|SA)\d$/;
             parts.forEach(part => {
                 if (part.startsWith('SLP')) {
                     decoded.push(`  - ${decodeSlp(part)}`);
+                } else if (obscurationRegex.test(part)) {
+                    decoded.push(`  - ${decodeObscurationRemark(part)}`);
                 } else if (part.match(/^([A-Z]{2}\d)+$/)) {
                     decoded.push(`  - ${decodeCloudTypesRemark(part)}`);
                 } else if (weatherRegex.test(part)) {