chore(git): ignore custom documentation files

Add AGENTS.md and CLAUDE.md to .gitignore to exclude project-specific documentation files.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

crates/platform/config/tests/precedence.rs

@@ -0,0 +1,19 @@
+use config_agent::{load_settings, Settings};
+use std::{env, fs};
+
+#[test]
+fn precedence_env_overrides_files() {
+    let tmp = tempfile::tempdir().unwrap();
+    let project_file = tmp.path().join(".owlen.toml");
+    fs::write(&project_file, r#"model="local-model""#).unwrap();
+
+    unsafe { env::set_var("OWLEN_MODEL", "env-model"); }
+    let s = load_settings(Some(tmp.path().to_str().unwrap())).unwrap();
+    assert_eq!(s.model, "env-model");
+}
+
+#[test]
+fn default_mode_is_plan() {
+    let s = Settings::default();
+    assert_eq!(s.mode, "plan");
+}