Upstream ik_llama.cpp commit e0596bf6 ("Autoparser") changed
common_params_sampling::grammar from std::string to a common_grammar
struct (type + grammar), which broke our two direct accesses:
- JSON ingest fed the field through json_value<common_grammar>(...),
for which nlohmann has no from_json adapter.
- JSON export emitted the struct directly, for which nlohmann has no
to_json adapter.
Wrap the incoming JSON string in common_grammar{COMMON_GRAMMAR_TYPE_USER, ...}
and serialize via the inner .grammar member, mirroring upstream's
examples/server/server-context.cpp.
Also bump IK_LLAMA_VERSION to 286ce324baed17c95faec77792eaa6bdb1c7a5f5
so the local-ai side lines up with the dependency bump in #9496.
Assisted-by: Claude-Code:claude-opus-4-7
