feat: Add decoding for PCPN past hour remarks

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

metar.html

@@ -344,6 +344,15 @@
                         return { consumed: 3, text: `  - DENSITY ALT ${altFeet}: Density altitude ${altitude} feet` };
                     }
                 },
+                // PCPN remark
+                {
+                    match: p => p[0] === 'PCPN' && p.length > 3 && p[1].endsWith('MM') && p[2] === 'PAST' && p[3] === 'HR',
+                    decode: p => {
+                        const amount = p[1].replace('MM', '');
+                        const raw = `PCPN ${p[1]} PAST HR`;
+                        return { consumed: 4, text: `  - ${raw}: Precipitation ${amount} mm in the past hour` };
+                    }
+                },
                 // Cloud remarks
                 {
                     match: p => cloudTypes[p[0]] || p[0] === 'ACC',