fix(cli): pass --model flag to ConfigOverrides in run command

Fixes bounty issue #1485

The --model CLI flag was being captured but ignored because run_cmd.rs
used Config::default() instead of Config::load_sync() with the model
override. This change creates ConfigOverrides with the model and cwd
fields from CLI arguments, ensuring CLI flags take precedence over
agent defaults.

Author: factorydroid

cortex-cli/src/run_cmd.rs

@@ -398,8 +398,13 @@ impl RunCli {
         let is_json = matches!(self.format, OutputFormat::Json | OutputFormat::Jsonl);
         let is_terminal = io::stdout().is_terminal();
 
-        // Create or resume session
-        let config = cortex_engine::Config::default();
+        // Create or resume session with CLI overrides
+        let overrides = cortex_engine::ConfigOverrides {
+            model: self.model.clone(),
+            cwd: self.cwd.clone(),
+            ..Default::default()
+        };
+        let config = cortex_engine::Config::load_sync(overrides).unwrap_or_default();
 
         // Initialize custom command registry if not already initialized
         let project_root = self.cwd.clone().or_else(|| std::env::current_dir().ok());