v0.3.0

Added

• env of run(), ask(), open() and startPane() can remove an inherited variable: a value
  of undefined (or null) drops it from the environment of the CLI (EnvOverrides). A host that
  runs with NODE_ENV=production no longer passes it on to every agent, where npm install skips
  devDependencies. In a pane it is an unset in the pane's script, so it works on a tmux server
  that was started with the variable, and a server started by the call does not get it at all.

Changed

• open() and startPane() give system a real slot where the CLI has one, instead of the first
  user message: Codex gets -c developer_instructions=…, OpenCode gets the system prompt of its
  build and plan agents through OPENCODE_CONFIG_CONTENT (it replaces OpenCode's own base
  prompt for them). A system without a prompt now opens Codex and OpenCode with no first
  message. Antigravity has no such slot and keeps the instructions in front of its first message.
  OpenPlan.env carries what the plan needs in the CLI's environment.