Allow the excluded directories to be configured

We have a "build" directory in one of our projects that apparently is on an internal list of folders (along with out, dist, node_modules) that is ignored by the listdirectory tool of the Q Integration.

This also prevents files in these directories from being explicitly @ mentioned into the context.

Please add a way to configure the excluded directories.

Start by locating the Q Integration listdirectory tool and its internal excluded-directory list, including the existing entries such as build, out, dist, and node_modules. Trace how the same filtering affects explicit @ mentions, then verify that excluded directories can be configured while existing defaults continue to work.

Written by the indexing model from the issue text.