refactor(cli): split doctor/model-resolution and run/events into focused modules

Doctor checks:
- model-resolution-cache.ts, model-resolution-config.ts
- model-resolution-details.ts, model-resolution-effective-model.ts
- model-resolution-types.ts, model-resolution-variant.ts

Run events:
- event-formatting.ts, event-handlers.ts
- event-state.ts, event-stream-processor.ts

src/cli/run/index.ts

@@ -4,4 +4,6 @@ export { createServerConnection } from "./server-connection"
 export { resolveSession } from "./session-resolver"
 export { createJsonOutputManager } from "./json-output"
 export { executeOnCompleteHook } from "./on-complete-hook"
+export { createEventState, processEvents, serializeError } from "./events"
+export type { EventState } from "./events"
 export type { RunOptions, RunContext, RunResult, ServerConnection } from "./types"