A diff renderer that restructures the diff — into columns, or with the
+/- markers replaced by colour — leaves us no way to tell which line of
which file a rendered row came from, which is what acting on the row
requires. The OSC 1717 protocol has the renderer say so directly: it
prefixes each line it renders with a record naming the file and the
line's position in the old and new versions of it.
Attach each record to the cells it precedes, so that a row's records
survive wrapping and the columns of a side-by-side rendering, and hand
them to readers together with the row's text: the two have to describe
the same buffer, and a re-render can rebuild it between two reads.
Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>