Add the variable OPS_DIR and OPS_FILE in ops

## Why you need it?
We need a variable OPS_DIR pointing to the directory where the current opsfile resides.
This is because if you change for example to $OPS_PWD you may beed to refer to the original folder of the opsfile, for example to run

`uv --directory $OPS_DIR run python main.py`

## How it could be?
Add the OPS_DIR of the taskfile you found to the environment and document it
Also OPS_FILE to point to the current opsfile.yml is useful

The issue names the current opsfile.yml and gives main.py as the example command target. Start by locating where the ops taskfile is found and its environment is assembled, then review the related documentation. Done means OPS_DIR points to the taskfile directory and OPS_FILE points to the current opsfile.yml.

Written by the indexing model from the issue text.