Add ReasoningMode type (off/on/stream) to AgentOptions and related
config types. Add extractThinking() for extracting thinking content
blocks from LLM responses, mirroring the existing extractText() pattern.
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
AsyncAgent now subscribes to pi-agent-core events (message_start,
message_update, message_end) and forwards incremental text deltas
through a stream callback. Hub registers the callback and sends
stream payloads to the requesting client via Gateway.
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>