The core runtime — manages API communication, tool execution, authentication,
and streaming for all SynapsCLI binaries (chat, chatui, server, agent, watcher).
Emit an after_tool_call event and return the tool output to record in
history — either the original output, or a Replace { output }
substituted by an extension transform hook (compression, redaction,
summarization). The runtime tool name is included when it differs from the
API-safe name.