Restore launch and project-dotenv LangSmith settings for user commands.
Precedence, highest first: the launch shell the user started dcode from,
then the project .env. The global profile .env is deliberately excluded,
because it configures the agent rather than the user's own commands.
Also pops the client-to-server carrier and every DEEPAGENTS_CODE_-prefixed
selector, so agent.py can pass the result with inherit_env=False.
Environment for user commands, modified in place.
Project directory whose .env supplies the lower layer.
Falls back to the mapping bootstrap captured for this process.
