fix(checkpoint): validate PEFT adapter-only state (#3501)

* fix(ci): keep Nemotron Flash robustness on TP1

Signed-off-by: Alexandros Koumparoulis <akoumparouli@nvidia.com>

* test(ci): isolate Qwen MoE checkpoint integrity gates

Signed-off-by: Alexandros Koumparoulis <akoumparouli@nvidia.com>

* test(ci): diagnose Qwen source parity instability

Signed-off-by: Alexandros Koumparoulis <akoumparouli@nvidia.com>

* test(checkpoint): compare PEFT adapter-only state

Signed-off-by: Alexandros Koumparoulis <akoumparouli@nvidia.com>

* test(ci): verify Qwen source expert weights

Signed-off-by: Alexandros Koumparoulis <akoumparouli@nvidia.com>

* test(ci): tolerate FSDP expert parameter prefixes

Signed-off-by: Alexandros Koumparoulis <akoumparouli@nvidia.com>

* test(ci): inspect Qwen expert state dict

Signed-off-by: Alexandros Koumparoulis <akoumparouli@nvidia.com>

* test(ci): remove Qwen parity diagnostics

Signed-off-by: Alexandros Koumparoulis <akoumparouli@nvidia.com>

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Signed-off-by: Alexandros Koumparoulis <akoumparouli@nvidia.com>