Fix alias output naming and improve Spike I/O diagnostics

Problem

The tracer's output naming step (Step 3 in NKIPyKernel._build_code) used a truthiness check (if not r.backend_tensor.name) to decide whether to assign the canonical
output{idx} name. This failed when a non-aliased output tensor already carried a name from tracing (e.g. "intermediate0" from an np.add result). The tensor kept
its intermediate name, causing a mismatch between the NEFF I/O table and what callers pass to kernel(inputs={...}, outputs={...}).

This was discovered during sglang-nkipy integration with the stable neuronx-cc 2.23.6484.0 compiler, where three kernel call patterns broke:

• Standalone aliased kernels (e.g. update_kv_cache): NEFF input renamed to kv_cache.must_alias_input but callers still passed kv_cache
• Fused graphs with aliased params (e.g. prefill_pre_moe): aliased output named kv_cache shifted other outputs to output1, output2, ...
• Broken-identity aliases (e.g. prefill_post_moe): mutated param passed through an NKI wrapper that breaks tensor identity, causing the tracer to auto-append a 3rd
  output

Debugging these required extracting NEFF I/O names from HLO protobuf binaries because Spike's _validate_io only produced a bare KeyError.

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