ui : trim whole-blob scans in tool block headers
Tool block headers parsed their entire blobs at mount, even collapsed,
and most tool results and args are large plain text or embedded file
content: skip JSON.parse unless the blob starts with a JSON container,
prefilter search-result extraction with a Title:/URL: substring check,
and match the end-anchored exit-code marker against only the tail of exec
outputs.
Assisted-by: pi:zai-org/GLM-5.3
