convert : export YaRN scaling parameters for PLaMo-3 (#29528)
Recent PLaMo-3 models use YaRN, while some earlier PLaMo-3 models do not.
The recent PLaMo-3 store their YaRN settings as flat config keys
(rope_scaling_factor, initial_context_length) and build the dict at runtime
in Plamo3Config.rope_parameters. The current converter misses these settings
and writes plain RoPE metadata to GGUF. Mirror the runtime settings into
rope_parameters so the corresponding rope.scaling.* is written to GGUF.
