Fix initialization of SND_UNA to ISN

[danielinux]

• related test
  wolfIP_sock_accept() was failing to set snd_una to the ISN

Fenrir/239

[Copilot]

Pull request overview

Fixes TCP sender state initialization when accepting incoming connections so snd_una correctly starts at the connection’s ISN (preventing invalid sequence ordering), and adds a regression unit test.

Changes:

• Initialize newts->sock.tcp.snd_una to the initial sequence number during wolfIP_sock_accept().
• Add a unit test that validates snd_una starts at ISN and remains <= seq after SYN-ACK advances seq.
• Register the new test in the unit test suite.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
src/wolfip.c	Initializes snd_una on the accepted TCP socket to ensure correct ISN-based sender state.
src/test/unit/unit.c	Adds and registers a regression test covering snd_una initialization during accept().

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[gasbytes]

lgtm, confirmed fix locally via gh cli.