Smarter assistant python pkg install

[nstrayer]

Note

This is the same as #8289 just applied to main instead of the release branch.

Addresses #8174.

Adds a new installPythonPackage tool that enables the Assistant to directly install Python packages instead of suggesting !pip commands that don't work in Positron's environment. The Assistant can now handle package installation requests by invoking the appropriate package manager (pip, uv, conda) through the integrated tool.

Note: This may be way too intense of a fix for a simple behavior change. Not at all married to the whole new tool at all.

Release Notes

New Features

• N/A

Bug Fixes

• Assistant can now directly install Python packages instead of suggesting non-functional
  !pip commands

QA Notes

Ask the Assistant to install Python packages like palmerpenguins and plotnine. The Assistant should now use the built-in installation tool rather than suggesting !pip commands.

Test in assistant

# Ask: "Install palmerpenguins and plotnine for me"
# Expected: Assistant uses the installPythonPackage tool to install packages directly
# Packages should be installed successfully without user needing to run terminal commands

The Assistant should no longer suggest !pip install commands and instead handle package installation automatically using the new tool.

[github-actions]

E2E Tests 🚀
This PR will run tests tagged with: @:critical

^{readme  valid tags}