fix(android): detekt ReturnCount on PasswordViewModel.change (3/2)

Combined the three early-bail checks (isChanging guard, empty-fields
validation, mismatch validation) into one when-expression with a
single return. Sentinel empty-string distinguishes "silent no-op
because already changing" from "user-facing validation error".

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

android/app/src/main/java/com/fabledsword/minstrel/settings/ui/PasswordViewModel.kt

@@ -39,13 +39,16 @@ class PasswordViewModel @Inject constructor(
 
     fun change() {
         val s = internal.value
-        if (s.isChanging) return
-        if (s.current.isEmpty() || s.next.isEmpty()) {
-            internal.update { it.copy(message = "All fields required.") }
-            return
+        val validationError: String? = when {
+            s.isChanging -> "" // sentinel: silent no-op
+            s.current.isEmpty() || s.next.isEmpty() -> "All fields required."
+            s.next != s.confirm -> "New passwords do not match."
+            else -> null
         }
-        if (s.next != s.confirm) {
-            internal.update { it.copy(message = "New passwords do not match.") }
+        if (validationError != null) {
+            if (validationError.isNotEmpty()) {
+                internal.update { it.copy(message = validationError) }
+            }
             return
         }
         viewModelScope.launch {