Marker standing in for lines dropped from the middle of a head/tail preview.

Shared by _message_eviction._create_content_preview and the capture wrapper in backends.sandbox so both emit identical marker text.

Never scan preview text for this marker to detect truncation: output can contain a literal marker line. Producers report marker presence out of band instead (see ExecuteOffloadResult.preview_has_truncation_marker).

Note: middleware.filesystem._LEGACY_TOO_LARGE_TOOL_MSG keeps a frozen copy of the old wording for a deprecated import and deliberately does not use this template.