`"a" + x + "b" + "c" + "d"` used to emit 4 Plus() calls because
the parser builds a left-leaning chain and no pair was
literal+literal. Add a reassociation step inside foldLiteralTree:
when the outer shape is `(Y + strlit1) + strlit2`, rewrite as
`Y + (strlit1+strlit2)` so the tail literals collapse. Also run
foldLiteralTree on the root BinaryExpr in emitExpr so the
outermost reassoc fires (was only running on children).
Verified: the 4-Plus case now emits 2 Plus calls (`"a" + x + "bcd"`).
FiveSql2 43/43, Harbour compat 56/56.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
CharlesKWON
7e4079f845