fix: recognize yen in currency conversions

README.md

@@ -100,6 +100,7 @@ sqrt(144)
 32 f to c
 1 GiB to MiB
 100 USD to DKK
+1000 yen to DKK
 0.5 BTC to ETH
 ```
 
@@ -109,6 +110,8 @@ Convert length, mass, temperature, volume, duration, speed, area, and data with
 
 Currency and crypto conversions require internet access and use [currency-api](https://github.com/fawazahmed0/exchange-api). These are **daily rates, not live market prices**; the snapshot date is shown with the answer. Treat them as estimates, not trading or payment quotes. Fetch failures show an error rather than silently using old rates; change the query to retry.
 
+`yen` is accepted as an alias for `JPY` in either conversion direction, case-insensitively.
+
 Rates are shared across queries and refreshed on the next currency query after the local day changes. While refreshing, a cached answer remains copyable and is labeled stale. Leaving the query or dismissing the launcher does not cancel that shared refresh.
 
 `ConjureKit.CurrencyCalculation` owns this lifetime policy; the launcher renders its result. Its checks use an injected clock and scripted rate fetches.

Sources/ConjureKit/Calculator.swift

@@ -105,6 +105,7 @@ public enum Calculator {
 
     private static func currencyCode(_ text: String, rates: CurrencyRates?) -> String? {
         let code = text.lowercased()
+        if code == "yen" { return "jpy" }
         guard (2...12).contains(code.utf8.count),
               code.utf8.allSatisfy({ (97...122).contains($0) || (48...57).contains($0) }),
               ConversionUnit.parse(text) == nil else { return nil }

Tests/ConjureKitTests/CurrencyTests.swift

@@ -11,6 +11,21 @@ func calculatorCrossConvertsCurrencyExpressionsAndPreservesSnapshotDate() throws
     #expect(result.detail == "2*50 USD → DKK · Daily snapshot 2026-01-02")
 }
 
+@Test
+func calculatorConvertsYenAsJPYInEitherDirection() {
+    let snapshot = CurrencyRates(date: "2026-01-02", rates: ["eur": 1, "jpy": 160, "dkk": 8])
+    for (query, expected) in [
+        ("1000 yen to dkk", "50 DKK"),
+        ("1000JPY to DKK", "50 DKK"),
+        ("1000YeN in dkk", "50 DKK"),
+        ("50 DKK as yen", "1000 JPY"),
+        ("2*500 yen to JPY", "1000 JPY"),
+    ] {
+        #expect(Calculator.isCurrencyQuery(query), "\(query)")
+        #expect(Calculator.evaluate(query, currencyRates: snapshot)?.copyValue == expected, "\(query)")
+    }
+}
+
 @Test
 func calculatorConvertsFiatAndCryptoWithCaseInsensitiveSeparators() {
     let snapshot = CurrencyRates(date: "2026-01-02", rates: [