Complete /todos actions and todo ids, session ids for /resume|/delete
(from cache after /sessions), /rounds hints, and --flags. Pass prior
tokens so multi-arg completion works.
Register REPL slash commands as a Click Group (params, UsageError, help).
Dispatch via awaitlet.async_def so sync command bodies can awaitlet()
async memory/confirm work. Completer and /help derive from the registry.
Decode and stream reasoning_content as ReasoningDeltaEvent; keep it on
assistant messages. CLI shows dim reasoning, toggles stream/verbose, and
prints full tool results when verbose.
NCBM