fix: validate params_list length matches components in instantiate_pi…

[areychana]

Reference Issues/PRs

fixes #168

What does this implement/fix? Explain your changes.

instantiate_pipeline was silently accepting a params_list longer than components the extra param dicts got validated with comp_name=None and passed to the executor without any error.

So i added a length check in src/sktime_mcp/tools/instantiate.py before the validation loop so that mismatched lengths return a clear error message instead of passing through silently.

Does your contribution introduce a new dependency? If yes, which one?

no.

What should a reviewer concentrate their feedback on?

• The length check added in instantiate.py around line 195
• The error message format that is consistent with existing error messages in the same file

Any other comments?

This bug was originally flagged in issue #35. Raising a dedicated fix since it's a clear
validation gap, invalid input was passing through silently to the executor.

PR checklist

• I've added unit tests and made sure they pass locally.