[BlivionIaG]

Draft: GPU validation pending. Merges cleanly into rdna_extras (branch is 189 commits behind).

Fork commits:

• f53fd9e74d opt-in config probe for Qwen4-family checkpoints (vllm/models/qwen4_prep/config_probe.py)
• 142c93cae4 config-to-stage-graph planner for the Qwen4 monokernel (qwen4_prep/mono_plan.py)
• 962054a6f5 opt-in dense MLP for Qwen4 checkpoints without experts (common/dense_mlp.py, mlp_selection.py)
• c3971d2c89 test fix (TP group init for the dense MLP meta tests)

Upstream backports (applied in order without conflicts):

• 22196687e9 [Kernel] Qwen4Exp: compute HyperConnection and PLE gate row offsets in int64 vllm-project/vllm#64820 int64 HyperConnection / PLE gate row offsets (amd/ops/hc.py, nvidia/ops/hc.py)
• d92580ced1 [Bugfix][Qwen4Exp] Reserve QSA indexer prefill workspace during memory profiling vllm-project/vllm#60490 reserve the QSA indexer prefill workspace during memory profiling
• b1938a5414 [Bugfix][Model] Qwen3.8-Flash-Next: load checkpoints with quantized q/k/v and a BF16 QSA indexer vllm-project/vllm#62318 Flash-Next: load checkpoints with quantized q/k/v and a BF16 QSA indexer
• 4c217d501b [Qwen4Exp] PLE disk offload vllm-project/vllm#59958 PLE disk offload (ple_offload_mode config surface)

Touches the production Flash-Next path: vllm/models/qwen4_exp/amd/model.py and common/ngram_embedding.py.

Checks so far: py_compile on every touched file; the CPU tests in tools/rdna/qwen4/ (config probe, dense MLP, mono plan).

Before ready:

• PLE offload overlap: [Qwen4Exp] PLE disk offload vllm-project/vllm#59958 overlaps the fork's PLE CPU/disk sidecar (vllm/v1/ple_offload/, VLLM_PLE_CPU_OFFLOAD, VLLM_PLE_QUANT_DIR). Readiness doc: keep the sidecar, take only the config surface, never run two offload mechanisms. Confirm the default path still goes through the sidecar.
• GPU validation (docs/rdna2/qwen4/readiness.md, table 'GPU validation: pending'): compiled F&P boot of flashnext-mtp2 and flashnext-mtp0 (PLE int4), greedy probes, PPL, prefix cache, 16k/1k c8 vs rdna_extras, 0 faults.
• Rebase: merge rdna_extras in first.