vectorise tool should allow the LLM to call vectorise without params

[e2r2fx]

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.

[Davidyz]

The thing is, some providers are more "sensitive" than others about the JSON schema. Some of them only support a subset of the schema definition, and it's usually not very well documented. The current schemas are what I've settled on that made different providers happy. Now that the built-in tools in codecompanion.nvim have stablzed, I can try to use them as a reference to improve all the VectorCode schemas (not just the vectorise tool).

EDIT: tracking this in #273