Add mechanism #2 to GetDiffLineInfo: when a patched pager annotated each diff
line with OSC 456 metadata, read it back as the first backend, ahead of the
buffer parser (#1) and the lazygit-edit hyperlink. It is strictly higher
fidelity -- it carries the side explicitly, so it serves the renderings #1
cannot parse (delta's default mode, --line-numbers, diff-so-fancy) and conveys
deletions, which the hyperlink can't.
The host advertises the protocol versions it understands by setting
EMIT_OSC456_METADATA on the pager subprocess; a pager that doesn't understand
it ignores the variable, so this is safe to set unconditionally.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>