fix: make Linux/WSL terminals, venvs and package management work end to end

[tusharbana-ansys]

Summary

Closes #591.

On Linux, and especially WSL, most actions failed silently because the app only ever launched gnome-terminal. This PR adds terminal detection with clear errors. It also fixes Linux bugs found while testing end to end: library leaks into terminals, package installs targeting the wrong Python, venvs created without pip/uv, and an RHEL/Fedora installer that reported false success.

Fixes

Terminal launching (linux_functions.py)

• Detect the first available terminal instead of hardcoding gnome-terminal. Supported: gnome-terminal, konsole, xfce4-terminal, mate-terminal, tilix, xterm, x-terminal-emulator.
• Launch with subprocess argument lists instead of os.system(), which also fixes shell-quoting issues.
• If no terminal is found, raise NoLinuxTerminalError with an install hint for the distro (sudo apt-get install xterm or sudo dnf install xterm).
• Start terminals with the user's LD_LIBRARY_PATH, not the frozen app's bundled one. Before, commands in these terminals loaded the app's own OpenSSL and other libraries, which broke ssl in Python built from source and could break system tools. This also affected gnome-terminal in v0.6.3.

Error reporting

• Console, launch and package actions show an error dialog instead of doing nothing (installed_table.py).
• Uninstall shows an error if the uninstaller can't be launched (uninstall.py).
• Venv creation no longer reports success after a failure. It checks that <venv>/bin/python exists and removes the empty folder so the same name can be reused (create_virtual_environment.py).

Package management on Linux (linux_functions.py, installed_table.py)

• Base Python: install into the selected interpreter (uv pip --python <path>) instead of --system. --system picked the OS Python: on Ubuntu 22.04 it installed into the OS Python, and on Ubuntu 24.04 and Fedora it failed with "externally managed". The interpreter's bin folder now comes first on PATH.
• New venvs: created with uv venv --seed, and pip and uv are installed into them. Before, venvs had neither, so uv pip ... failed with "command not found".
• Existing venvs: pip and uv are updated with the venv's own interpreter. Before, the command tried to run the venv folder itself. Venvs created by older versions get pip via ensurepip.
• Removed the duplicate pip/uv update on Linux.

Other

• find_miniforge_linux(): read CONDA_PYTHON_EXE from the environment. A shell pipe passed without shell=True meant system conda was never detected.

Installers and docs

• linux/debian/installer.sh, docs: require gnome-terminal instead of the full gnome desktop, and add a note that xterm is enough on WSL.
• installer_CentOS.sh (also shipped as installer_Fedora.sh):
  • use dnf, falling back to yum; exit with an error if neither exists;
  • require mesa-libGL, mesa-libEGL and xcb-util-cursor, without which the app can't open its window;
  • detect installed groups with group list --installed, and fall back to the development-tools group ID, which dnf5 (Fedora 41+) requires;
  • exit with an error instead of printing "Installation success" when dependency or package installation fails.
• Docs: list the extra RHEL/Fedora packages; the Fedora command uses the development-tools group ID.

Testing

• Unit tests: cover terminal detection, the no-terminal error and install hint, and LD_LIBRARY_PATH handling for both launch modes. All 23 tests pass, and all pre-commit hooks pass.
• Manual testing: apps frozen from this branch, run on fresh WSL distros as a non-root user and driven through the GUI with the keyboard. Results were checked on disk.

Distro	Terminal	Verified
Ubuntu 22.04	gnome-terminal	Base-Python install goes into the Ansys Python (OS Python untouched); new and old venvs; Console has no leaked LD_LIBRARY_PATH
Ubuntu 24.04	gnome-terminal	Base and venv installs; venv creation; base and venv Console
AlmaLinux 9 (RHEL 9 family)	gnome-terminal	Installer: reinstall fails correctly, clean install, missing dependency installed; base and venv installs; venv creation
Fedora 43 (dnf5)	xterm	No-terminal error; Python 3.11 source build with working ssl; venvs (including conda); JupyterLab; full installer run with dnf5

• Baseline: on all four distros without a terminal, v0.6.3 fails silently, while this PR shows an error dialog.

Out of scope (existing behavior)

• Apart from venv creation, the app still doesn't check whether commands run in the terminal succeeded; it can only tell that the terminal opened.
• gnome-terminal can fail with "Could not connect" when the WSL user session hasn't started its message bus; wsl --shutdown fixes it.

[tusharbana-ansys]

Although automated tests have passed, I am still testing this manually on each supported distro. Please do not merge yet.
cc - @RobPasMue

[RobPasMue]

Sounds good! Keep me posted. Once it's ready to review and tested manually I will review :)

[RobPasMue]

LGTM!