[Stack 3/4][Draft] Gemma4 core Gemini INC review fixes

[lesj0610]

internal stacked PR for branch organization only.\n\nthis layer isolates the direct Gemini review fixes in inc.py from upstream PR vllm-project#40281.\n\nmain contents:\n- remove invalid qweight.tp_rank access\n- import and use get_tensor_model_parallel_rank()\n- replace register_buffer(..., None) cache init\n- vectorize g_idx creation\n\nupstream-facing branch: lesj/gemma4-core-pr\nupstream PR: vllm-project#40281

[github-actions]

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[lesj0610]

superseded by the finer-grained Gemma4 core stack in #16-#22.