[Bug]: Relative paths for background images does not function as expected

[Printoiid]

Current Behavior

When defining a background image in any preset, it's impossible to use a relative path when referencing a JPG image.

EG
Is valid:

...
     "bg": "url('~/.config/waveterm/presets/picture.jpg')"
...

Is not valid:
(assuming the PWD is in the /presets directory.)

...
     "bg": "url('./picture.jpg')"
...

Expected Behavior

Relative pathing from the /presets directory in ~/.config/waveterm/presets/ work, otherwise default to full defined path.

Steps To Reproduce

1. Create a new configuration in ~/.config/waveterm/presets on Linux.
2. Create a relative path with some image in a preset configuration. (See current behavior)
3. Attempt to change your background for the tab as that newly created preset configuration.

Wave Version

0.11.3

Platform

Linux

OS Version/Distribution

Mint 22.1

Architecture

arm64

Anything else?

No response

Questionnaire

• I'm interested in fixing this myself but don't know where to start
• I would like to fix and I have a solution
• I don't have time to fix this right now, but maybe later