Type 9 Constant-YOP: Implement exact constant table from docs.
Index = (YY<<2)|CC, value = 1<<idx for BO=01, -(1<<idx)-1
for BO=11. Special case idx=15: -32768 / +32767.
(was: simple cc with optional negate, completely wrong values)
Type 18: Fix DIS encoding to check for bit pattern 10 (was 01).
Verified all 8 modes against assembler: ENA/DIS for
AS, MM, BR, TI all correct.
Truncation guards: Use saved 'avail' from original op->size
instead of checking op->size after it was set to 3.
(was: always true, guards never triggered)
ae98262bb7