WASHINGTON — Hunter Biden offered Tuesday to testify publicly before Congress, striking a defiant note in response to a subpoena from Republicans and setting up a potential high-stakes face-off even as a special counsel probe unfolds and his father, President Joe Biden, campaigns for reelection.The Democratic president’s son slammed the subpoena’s request for closed-door testimony, saying it could be manipulated. But Rep. James Comer of Kentucky, the chairman of the House Oversight Committee, stood firm …