Executes a raw DDR blob in AArch64 Unicorn with configurable stub
byte (--stub 0x00 / 0xFF) returned for every MMIO read. Intent:
gate real-hardware flashing behind "blob doesn|t crash the emu
under either stubbing regime."
Validated against rk3588_ddr_lp4_1848MHz_lp5_2112MHz_v1.19.bin
(stock) and patch_timeouts_v3.py --sites all output: both reach
max_pc=0xe0 and HALT cleanly via the return stub at RET_STUB,
identical under 0x00 and 0xFF stubs.
Phase 2 of test harness task #31. Phase 1 (spi_check.py,
structural RKNS validation) committed earlier.
