What would you like to be added?

Adds native recognition for JetBrains IDE as a supported IDE environment.

Why is this needed?

Currently, Gemini CLI restricts IDE integration features to environments where TERM_PROGRAM is vscode (or other hardcoded values). This forces 3rd-party integrations like jetbrains-ide-companion to mock VS Code by spoofing environment variables to enable core features, otherwise it could not be discovered by Gemini CLI.

For some reason, the process detection is not working properly on windows/linux (, reported by users here JetBrains Plugin Review and here #9273 , and a few other bug report email i've received), which making this native IDE detection logic a MUST do for gemini-cli discover and connect to IDE via environmental variables instead of port info file.

This PR adds JetBrains IDE Series to the IDE_DEFINITIONS and updates the detection logic to recognize TERMINAL_EMULATOR=JetBrains-JediTerm as a first-class supported environment.

Additional context

Inspired by #16083