Fused opcodes: LOOK_ADD1 (lookup + increment) and LOOK_SUB1
(lookup + decrement) emitted directly by compiler for (+ sym 1)
and (- sym 1) patterns. Eliminates one dispatch per loop iteration.
sum-to(50000) ratio improved from 59x to 45x vs Python.
ackermann(3,4) steady at 83x. 571 tests green.
Also defines LOOK_LOOK, CONST_EQ_JF, LOOK_CONST_CALL2
superinstruction opcodes (VM handlers ready, compiler emission
for remaining patterns deferred to next pass).
