The tbasic, kilo, and ed apps unconditionally overrode HEAPADDR/HEAPSIZE
with ZPU BRAM addresses (0x1FFF5000+0x33000=0x20028000) that exceed the
K64F app CODE region. Wrapped overrides in ifeq ($(__ZPU__),1) so K64F
builds use the default heap/stack calculated by build.sh.
Also disabled mbasic K64F build (heap overrides + code size exceed CODE
region) — mbasic was already disabled for ZPU.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>