Memory & data-corruption debug for tt-emule

Distills the diagnostic playbook used across rounds 7-12. Targets the failure mode "kernel runs, no crash, but output bytes don't match input". Most fixes land in include/jit_hw/api/dataflow/, include/jit_hw/llk_pack.h, include/jit_hw/api/compute/common.h, or tt_metal/impl/emulation/emulated_program_runner.cpp.

For pure JIT-compile failures (missing shim), use /compute-llk-bringup. For missing API surface, use /implement-mock.

When to invoke

• "ATOL > 1e-3" / "PCC failure" / "max diff X" on a kernel that previously worked or that runs to completion.
• "Output is mostly correct but has wrong regions" / "some rows are wrong" / "some tiles are zero".
• "Sharded → interleaved" (or vice versa) data movement is wrong.
• "Output bytes are zero" where they shouldn't be.