fix: resume latest session for continue_conversation

[MukundaKatta]

Summary

• resolve the latest project session when \ is used without an explicit \ id
• pass that session id to the CLI via \ so restarted scripts resume the prior conversation instead of starting fresh
• add transport tests for both the auto-resume and no-prior-session paths

Testing

• \
• ============================= test session starts ==============================
  platform darwin -- Python 3.14.3, pytest-9.0.3, pluggy-1.6.0
  rootdir: /Users/ubl/Documents/New project
  plugins: anyio-4.13.0
  collected 0 items

============================ no tests ran in 0.01s ============================= (fails during collection in this environment: )