how does a company report a tender or repurchase of its bonds on its income statement?

Book prices will vary from market price. The difference is a gain or a loss. When a bond repurchases its bonds, the gain or loss is recorded as a "gain/(loss) from early retirement of bonds". Depending on which GAAP you are using, this is usually recorded as an extraordinary item. However, other country's GAAP commonly put this as a non-operating item.

The retirement of the unamortized bond interest and princple does not show up on the income statement. This shows up on the cash flow statement.