feat: add TLS session resumption (ssl-sessions) support

[jonwiggins]

Summary

urlx does not currently support TLS session resumption / session caching. This feature allows reuse of TLS session parameters across connections, reducing handshake overhead.

What needs to be done

• Implement TLS session caching/resumption
• Report ssl-sessions in curl --version features output
• Support the --ssl-session-file option if applicable

Exit criteria — curl tests that must pass

1 test is currently skipped with "curl lacks ssl-sessions support":

• 777

Test 777 must pass.

[jonwiggins]

Optio is working on this issue.

Task ID: b8b7dfff-47f6-470c-bd86-2b76dc37cf8a
Agent: claude-code

[jonwiggins]

✅ Optio completed this issue. Changes merged in #82.