Each WHERE-expression Operand now records the byte span of the
terminal it was built from — the precise per-literal highlight
target for an expression WARNING (finishing ADR-0027 §2's
highlight/hint wiring). parse_operand captures MatchedItem::span;
the RowFilter::eq convenience constructor uses Operand::NO_SPAN.
PartialEq is hand-written to ignore the span — it is editor
metadata, so Command equality stays whitespace- and
position-independent, which the Expr test corpus relies on.
No behaviour change; 1100 tests still pass, clippy clean.
claude@clouddev1
426e80185f