(new): support Bot API 10.3

(fix): finalize v2 contracts
(tests): cover v2 migration
(doc): prepare release guidance

errors.go

@@ -76,6 +76,8 @@ var (
 	ErrCallbackDataLength = errors.New("callback data must be between 1 and 64 bytes")
 	// ErrInlineKeyboardRowTooLong reports a row exceeding the configured maximum.
 	ErrInlineKeyboardRowTooLong = errors.New("inline keyboard row exceeds maximum size")
+	// ErrInlineKeyboardMaxRow reports a non-positive row limit without explicit unlimited mode.
+	ErrInlineKeyboardMaxRow = errors.New("inline keyboard maximum row size must be positive")
 )
 
 var (