Fix forwarded slots detection on template slots

Editor assessment

fix(compiler-core) says forwarded slots detection on template slots was fixed, with the pull request in the header and a valid issue closure in the body. The scope and type fit, and the subject is imperative and unterminated. No explanation is given for what the detection got wrong, so the why is absent, but the subject names the exact mechanism affected and is understandable. Correct and publishable with a modest context gap.