feat(gateway): full Telegram+Discord integration with agent loop

Complete multi-platform gateway wiring:

config:
- [platform.telegram] section with bot_token
- [platform.discord] section with bot_token + guild_id
- Threaded through GyandootConfig → AgentConfig via typed structs

gateway:
- GatewayRunner::new(platforms) takes Vec<Box<dyn Platform>>
- start() spawns all platform pollers, merges receivers
- serve(agent) runs full message loop: receive → access control →
  typing indicator → session_turn() → platform.send()
- Ctrl+C graceful shutdown via tokio::select!

cmd_serve now:
1. Loads config, creates agent
2. Builds Telegram + Discord adapters from config
3. Starts gateway pollers
4. Enters serve loop until Ctrl+C

src/main.rs

@@ -364,19 +364,53 @@ fn load_and_convert_config(path: &std::path::Path) -> Result<gyandoot_core::conf
 }
 
 /// Start the gateway server for multi-platform sessions
-async fn cmd_serve(profile_name: &str, host: &str, port: u16) -> anyhow::Result<()> {
-    tracing::info!(
-        "Starting gateway server (profile={}, bind={}:{})",
-        profile_name, host, port
-    );
+async fn cmd_serve(profile_name: &str, _host: &str, _port: u16) -> anyhow::Result<()> {
+    tracing::info!("Starting gateway server (profile={})", profile_name);
 
-    let gateway = gyandoot_gateway::GatewayRunner::new();
+    let config = load_agent_config();
+    let agent = gyandoot_agent::agent_loop::AgentLoop::new(config.clone());
+
+    // Build platform adapters from config
+    let mut platforms: Vec<Box<dyn gyandoot_platform::Platform>> = Vec::new();
+
+    // Telegram
+    if let Some(tg) = &config.platform.telegram {
+        if !tg.bot_token.is_empty() {
+            platforms.push(Box::new(
+                gyandoot_platform::telegram::TelegramPlatform::new(&tg.bot_token),
+            ));
+            tracing::info!("Telegram platform added");
+        }
+    }
+
+    // Discord
+    if let Some(dc) = &config.platform.discord {
+        if !dc.bot_token.is_empty() {
+            platforms.push(Box::new(
+                gyandoot_platform::discord::DiscordPlatform::new(&dc.bot_token, dc.guild_id),
+            ));
+            tracing::info!("Discord platform added");
+        }
+    }
+
+    // Gateway
+    let mut gateway = gyandoot_gateway::GatewayRunner::new(platforms);
     gateway.start().await?;
-    tracing::info!("Gateway running on {}:{} — press Ctrl+C to stop", host, port);
+    tracing::info!("Gateway started — listening on platforms");
+
+    tokio::select! {
+        _ = tokio::signal::ctrl_c() => {
+            tracing::info!("Shutting down gateway...");
+            gateway.stop();
+        }
+        result = gateway.serve(&agent) => {
+            match result {
+                Ok(()) => tracing::info!("Gateway serve completed"),
+                Err(e) => tracing::error!("Gateway serve error: {}", e),
+            }
+        }
+    }
 
-    // Keep running until signal
-    tokio::signal::ctrl_c().await?;
-    gateway.stop().await;
     Ok(())
 }