Write() creates strokes that do not scale with font_size or scale

Nobody has claimed this yet.

## Description of bug / unexpected behavior
When calling the Write() animation, the cool effect (the growing stroke) appears to be hard-coded and not respect my font_size or the scale property of my MObject.

## Expected behavior
The increased stroke width of the Write() effect scales down if the text is smaller.

## How to reproduce the issue

Code for reproducing the problem

```py
Tex.set_default(font_size=9.6)
half = Tex("text goes here \frac{1}{2}")
self.play(Write(half))

```

## Additional media files

Images/GIFs

https://github.com/user-attachments/assets/51772287-2d22-4a97-ac7a-671eb79ac146

## Logs
Terminal output
rendering issue, so imo log is irrelevant.

## System specifications

System Details

- OS (with version, e.g., Windows 10 v2004 or macOS 10.15 (Catalina)): macOS 15.4
- RAM: 8GB
- Python version (`python/py/python3 --version`):Python 3.12.7
- Installed modules (provide output from `pip list`):
```
Package Version
---------------------- -----------
av 13.1.0
beautifulsoup4 4.13.3
click 8.1.8
cloup 3.0.7
cython 3.0.12
decorator 5.2.1
glcontext 3.0.0
isosurfaces 0.1.2
manim 0.19.0
manimpango 0.6.0
mapbox-earcut 1.0.3
markdown-it-py 3.0.0
mdurl 0.1.2
moderngl 5.12.0
moderngl-window 3.1.1
networkx 3.4.2
numpy 2.2.4
pillow 11.1.0
pycairo 1.27.0
pydub 0.25.1
pyglet 2.1.3
pyglm 2.8.1
pygments 2.19.1
pyobjc-core 11.0
pyobjc-framework-cocoa 11.0
rich 14.0.0
scipy 1.15.2
screeninfo 0.8.1
skia-pathops 0.8.0.post2
soupsieve 2.6
srt 3.5.3
svgelements 1.9.6
tqdm 4.67.1
typing-extensions 4.13.1
watchdog 6.0.0
```

LaTeX details

+ LaTeX distribution (e.g. TeX Live 2020): TeX Live 2025

## Additional comments

Start at the Write() animation entry point and reproduce the issue with the provided Tex("text goes here \\frac{1}{2}") example using font_size=9.6. Compare the rendered growing stroke at smaller font sizes and MObject scales; done means the stroke scales down with both properties.

Written by the indexing model from the issue text.