Shared formatter in sx_types.ml. Small integer-valued floats still print
as plain ints; floats outside safe-int range (|n| >= 1e16) now print as
%.17g (full precision) instead of silently wrapping to negative or 0.
Non-integer values keep %g 6-digit behavior — no existing SX tests regress.
Unblocks Number.MAX_VALUE / Math.pow(2,N) style tests in js-on-sx where
iterative float loops were collapsing to 0 at ~2^63.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
giles
b45a69b7a4