feat(channels): add send_progress option to control progress message delivery

Add a boolean config option `channels.sendProgress` (default: false) to
control whether progress messages (marked with `_progress` metadata) are
sent to chat channels. When disabled, progress messages are filtered
out in the outbound dispatcher.

nanobot/config/schema.py

@@ -168,6 +168,7 @@ class QQConfig(Base):
 class ChannelsConfig(Base):
     """Configuration for chat channels."""
 
+    send_progress: bool = False
     whatsapp: WhatsAppConfig = Field(default_factory=WhatsAppConfig)
     telegram: TelegramConfig = Field(default_factory=TelegramConfig)
     discord: DiscordConfig = Field(default_factory=DiscordConfig)