And the working directory in Travis is… /home/travis/build/<user>/<project>.
As you can see from the source, you can override this default by adding sonar.javascript.exclusions and/or sonar.typescript.exclusions to sonar-project.properties.
This is a bug (oversight) in the pattern matching behavior in my book. These patterns are meant to be matched against the part of the path under the project root rather than absolute path.