fix(frontend): fix knowledge hierarchy warning false positive
The condition item?.category && item.serviceKey !== 'just-chat' fired for ALL buttons with a category (8/9 CENTA buttons). Having a category is valid config, not a mismatch.
Changed to !item — warning only fires when a service label has no matching entry in selectedContextItems (actual config mismatch).
Cherry-picked from release/el-salvador-ds-port.