[FEAT] vectorise tool should allow the LLM to call vectorise without params

[Davidyz]

Discussed in #272

^{Originally posted by e2r2fx August 15, 2025}
The vectorise tool marks the project root and paths as required parameters, while allowing to pass empty strings when the model wants to use the defaults (use git as project root and no paths). This confounds several models. Suggestion, don't mark the parameters as required and be more clear with the description.