cfonts --gradient producing error with more than three colors

Hi, I have an interesting environment in which to debug because I'm sharing `$HOME` folders between two systems, one using Fedora 41 with the original `cfonts` program, and one running `python-cfonts` on Debian 13 (testing/trixie) installed with `pipx`.

Each system that has a clone of `$HOME` or `$ZSH` folder runs a `pretty_hostname` function to announce where I am.

TL;DR - `python-cfonts --gradient [colors]` appears to error when given more than 3 colors. **When I reduce the number of colors to 3, gradient appears as normal**

environment information for Debian machine:

```
❯ which python3 && python3 --version
/usr/bin/python3
Python 3.13.2

❯ which pipx && pipx --version
/usr/bin/pipx
1.7.1

❯ uname -rv
6.12.12-amd64 #1 SMP PREEMPT_DYNAMIC Debian 6.12.12-1 (2025-02-02)
```

Login banner argument:

```
cfonts "$(hostname)" --font "block" --gradient red,"#f80",green,blue --transition-gradient
```

The gradient colors are actually from an example pulled from the Fedora `cfonts` package documentation `/usr/share/doc/cfonts/README.md` line 356

```
355 │ ```sh
356 │ $ cfonts "text" --gradient red,"#f80",green,blue --transition-gradient
357 │ ```
```

Error output:

```
Traceback (most recent call last):
File "/home/avery/.local/bin/cfonts", line 8, in
sys.exit(main())
~~~~^^
File "/home/avery/.local/share/pipx/venvs/python-cfonts/lib/python3.13/site-packages/cfonts/cli.py", line 169, in main
say(args.text, **options)
~~~^^^^^^^^^^^^^^^^^^^^^^
File "/home/avery/.local/share/pipx/venvs/python-cfonts/lib/python3.13/site-packages/cfonts/core.py", line 373, in say
write = render(text, **options)
File "/home/avery/.local/share/pipx/venvs/python-cfonts/lib/python3.13/site-packages/cfonts/core.py", line 336, in render
output = paint_gradient(
output,
...<5 lines>...
transition,
)
File "/home/avery/.local/share/pipx/venvs/python-cfonts/lib/python3.13/site-packages/cfonts/core.py", line 221, in paint_gradient
styles = pen.get_gradient(gradient, max_index - min_index + 1, transition)
File "/home/avery/.local/share/pipx/venvs/python-cfonts/lib/python3.13/site-packages/cfonts/colors.py", line 179, in get_gradient
assert sum(color_steps) == steps - 1
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError
```

I see this `assert sum(color_steps) == steps - 1` statement at `cfonts/colors.py` line 169.

I am figuring something's up with my syntax, even though it's pulled straight from the original `cfonts` `README.md`. In an attempt to diagnose my syntax, I've tried using the following alterations:

- wrapping only `#f80` with double quotes (default)
- wrapping only `#f80` with single quotes
- making `#f80` `#F80`
- wrapping all colors with single and double quotes
- wrapping only the `#f80` with single and double quotes
- wrapping each color in single quotes and all colors with double quotes

Let me know if you have any ideas, I can try poking around at stuff.

PS: removing one of the colors of the gradient as workaround (no rush).

Reproduce the reported command `cfonts "$(hostname)" --font "block" --gradient red,"#f80",green,blue --transition-gradient`, then read `cfonts/colors.py` around `get_gradient` and `cfonts/core.py` around `paint_gradient`. Done means four or more gradient colors no longer trigger the reported AssertionError while the existing three-color behavior remains working.

Escrito por el modelo de indexación a partir del texto del issue.