fix(agent): use config-driven limits in run_tool_call_loop and trim_history

run_tool_call_loop used a hardcoded MAX_TOOL_ITERATIONS (10) and
trim_history/auto_compact_history used a hardcoded MAX_HISTORY_MESSAGES (50),
ignoring the user-configurable agent.max_tool_iterations and
agent.max_history_messages values in config.toml.

Meanwhile, agent.rs correctly reads from config — creating an inconsistency
where CLI single-shot mode respected config but the channel runtime and
interactive CLI loop silently ignored it.

Changes:
- Rename constants to DEFAULT_* to clarify they are fallback defaults
- Add max_tool_iterations parameter to run_tool_call_loop
- Add max_history parameter to trim_history and auto_compact_history
- Thread config.agent.max_tool_iterations through ChannelRuntimeContext
- Both CLI code paths now pass config values to run_tool_call_loop

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/channels/mod.rs

@@ -71,6 +71,7 @@ struct ChannelRuntimeContext {
     model: Arc<String>,
     temperature: f64,
     auto_save_memory: bool,
+    max_tool_iterations: usize,
 }
 
 fn conversation_memory_key(msg: &traits::ChannelMessage) -> String {
@@ -219,6 +220,7 @@ async fn process_channel_message(ctx: Arc<ChannelRuntimeContext>, msg: traits::C
             true, // silent — channels don't write to stdout
             None,
             msg.channel.as_str(),
+            ctx.max_tool_iterations,
         ),
     )
     .await;
@@ -1271,6 +1273,7 @@ pub async fn start_channels(config: Config) -> Result<()> {
         model: Arc::new(model.clone()),
         temperature,
         auto_save_memory: config.memory.auto_save,
+        max_tool_iterations: config.agent.max_tool_iterations,
     });
 
     run_message_dispatch_loop(rx, runtime_ctx, max_in_flight_messages).await;
@@ -1495,6 +1498,7 @@ mod tests {
             model: Arc::new("test-model".to_string()),
             temperature: 0.0,
             auto_save_memory: false,
+            max_tool_iterations: 10,
         });
 
         process_channel_message(
@@ -1536,6 +1540,7 @@ mod tests {
             model: Arc::new("test-model".to_string()),
             temperature: 0.0,
             auto_save_memory: false,
+            max_tool_iterations: 10,
         });
 
         process_channel_message(
@@ -1631,6 +1636,7 @@ mod tests {
             model: Arc::new("test-model".to_string()),
             temperature: 0.0,
             auto_save_memory: false,
+            max_tool_iterations: 10,
         });
 
         let (tx, rx) = tokio::sync::mpsc::channel::<traits::ChannelMessage>(4);