fix: #128 swap ours and theirs in Wallet.File.merge error (#132)

The IOException thrown by Wallet.File.merge on an id mismatch labelled the
other wallet's id as ours and this wallet's id as theirs, sending a reader
to the wrong side of the comparison. Swap the FormattedText arguments so
the label matches the value, and update the pinned assertion in
WalletTest.doesNotMergeWalletsWithDifferentId.

Closes #128

Co-authored-by: Claude <noreply@anthropic.com>

Author: bibonix

src/main/java/io/zold/api/Wallet.java

@@ -227,8 +227,8 @@ public Wallet merge(final Wallet other) throws IOException {
                     new UncheckedText(
                         new FormattedText(
                             "Wallet ID mismatch, ours is %d, theirs is %d",
-                            other.id(),
-                            this.id()
+                            this.id(),
+                            other.id()
                         )
                     ).asString()
                 );

src/test/java/io/zold/api/WalletTest.java

@@ -112,7 +112,7 @@ public void doesNotMergeWalletsWithDifferentId() throws IOException {
                 () -> wallet.merge(new Wallet.Fake(123L))
             ).getMessage(),
             Matchers.startsWith(
-                "Wallet ID mismatch, ours is 123, theirs is 5124095577148911"
+                "Wallet ID mismatch, ours is 5124095577148911, theirs is 123"
             )
         );
     }