feat(channel): pass conversation type through to agent gateway and persist in route

Propagate conversation type (direct/group/thread) from channel adapters
all the way to the agent prompt. Store conversation_type on bot_channel_routes
so the bot knows whether a message originates from a p2p chat, group, or thread.

Schema changes are folded into the 0001 init migration (destructive update).

db/migrations/0001_init.up.sql

@@ -207,6 +207,7 @@ CREATE TABLE IF NOT EXISTS bot_channel_routes (
   channel_config_id UUID REFERENCES bot_channel_configs(id) ON DELETE SET NULL,
   external_conversation_id TEXT NOT NULL,
   external_thread_id TEXT,
+  conversation_type TEXT,
   default_reply_target TEXT,
   metadata JSONB NOT NULL DEFAULT '{}'::jsonb,
   created_at TIMESTAMPTZ NOT NULL DEFAULT now(),

db/migrations/0002_channel_identity_avatar.down.sql

@@ -0,0 +1,2 @@
+-- 0002_channel_identity_avatar (down)
+ALTER TABLE channel_identities DROP COLUMN IF EXISTS avatar_url;

db/migrations/0002_channel_identity_avatar.up.sql

@@ -0,0 +1,3 @@
+-- 0002_channel_identity_avatar
+-- Add avatar_url column to channel_identities for sender profile display.
+ALTER TABLE channel_identities ADD COLUMN IF NOT EXISTS avatar_url TEXT;

db/migrations/0003_route_conversation_type.down.sql

@@ -0,0 +1,2 @@
+-- 0003_route_conversation_type (down)
+ALTER TABLE bot_channel_routes DROP COLUMN IF EXISTS conversation_type;

db/migrations/0003_route_conversation_type.up.sql

@@ -0,0 +1,3 @@
+-- 0003_route_conversation_type
+-- Add conversation_type column to bot_channel_routes for conversation context.
+ALTER TABLE bot_channel_routes ADD COLUMN IF NOT EXISTS conversation_type TEXT;