Accept set_route as model switch alias

[1jehuang]

Summary

• accept legacy set_route requests as an alias for set_model
• keep serializing model switch requests as set_model
• add a regression test for set_route deserialization

Fixes #295

Test plan

• cargo test -p jcode-protocol test_set_route_deserializes_as_set_model_compat_alias
• rustfmt --check crates/jcode-protocol/src/wire.rs crates/jcode-protocol/src/protocol_tests/misc_events.rs
• selfdev build / scripts/dev_cargo.sh build --profile selfdev -p jcode --bin jcode