Master moved the step's model route into the assembly context: the agent loop
fixes it per step and registers the prompt's provider variable from it, and
installModelSelection no longer takes a mutable selection. The tool-web
readiness fixture now registers that variable and passes the step's
modelSelection to each assembly.
AgentRegistry now needs the session projection registry, so the
web-search-deepseek initiator fixtures and the Loader composition in
chat-endpoint.spec.ts mount it, as master's own fixtures in this package do.
Yichen Jiang
2548bb4acf