How to modify existing lovelace component (source code?)

let me preface this by saying I’m very new to developing and as such am a little confused by what is goig on with the lovelace front end. I was hoping to edit the existing code of the “Thermostat Card” but I cannot for the life of my find the source code for this. In the past, if I wanted to modify an existing component I would just visit the home assistant github repository and copy/edit the code how I liked then put it in the custom components folder. I was hoping to do the same to the thermostat card so that I can increase/decrease the temperature by .5 degree increments instead of the current 1 degree increments since my thermostat entity is already set to .5 degree tolarance and reports in .1 increments. Any idease?

This is not recommended since your changes will be overwritten the next time you upgrade.
If you still want to do it you have to give some more information about your install since the location of the source code might be different depending on install method.
I think there is a custom thermostat card as well that you might want to look into instead. That will be easier to modify.

I am running HASS in a venv on rasbian (rasbian not hassbian). I would prefer to use the stock card as i like the aesthetic.

I’m looking for the same.
My goal is to change base Thermostat Card https://www.home-assistant.io/lovelace/thermostat/ to add second control to change (cold_tolerance, hot_tolerance) of Generic Thermostat https://www.home-assistant.io/components/generic_thermostat/

I’ve done a similar thing for the stock weather card. As far as I can tell, you have to keep an up to date development frontend repo and continually be building the frontend in each release. It is a PAIN.