xshape changes the geometry of a single table -- pivot, unpivot, transpose,
split one column into several, merge several into one, explode a delimited
cell into rows -- without ever changing, filtering, or aggregating a value.

Every input cell reappears unchanged, and a pivot errors out rather than
silently summing on a collision.  It shares the column-addressing dialect of
xled (letters, bracketed names, ranges), so the tools read as one language
with different verbs.
