Introduce a typed agent→gateway delivery contract so the gateway (not the
agent) decides how each streaming event is rendered per platform. Moves toward
smart-agent/smart-gateway separation while reproducing today's behavior exactly
in the base class.
- gateway/stream_events.py: typed event vocabulary (MessageChunk/Stop,
Commentary, ToolCallChunk/Finished, LongToolHint, GatewayNotice).
- gateway/stream_dispatch.py: GatewayEventDispatcher routes events through the
adapter; adapters can eat events they can't render (e.g. tool chrome on
plain-text platforms).
- gateway/platforms/base.py: render_message_event + format_tool_event default
hooks reproduce the historical emoji/preview tool formatting and consumer
delegation 1:1; adapters override for native rendering.
- gateway/platforms/telegram.py: send_draft now applies MarkdownV2 (format_message
+ parse_mode) with a plain-text fallback on BadRequest, fixing the jarring
raw-text→formatted shift when the draft finalizes as a real sendMessage.
- gateway/config.py: default streaming transport edit → auto. Safe globally:
adapters without draft support report supports_draft_streaming()==False and
transparently use edit, so only Telegram DMs gain native drafts.
Presentation-only contract — nothing rendered here is persisted to conversation
history, preserving cache/message-flow invariants.
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