feat: add config-owned direct skill submit path

Add fixed direct-submit skill loading from configured staged skills and validate directSubmitSkill early so malformed configs fail before routing.

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

tests/compat_config_test.rs

@@ -161,6 +161,60 @@ fn sgclaw_settings_default_to_compact_skills_and_browser_attached_profile() {
     assert_eq!(settings.skills_prompt_mode, SkillsPromptMode::Compact);
 }
 
+#[test]
+fn sgclaw_settings_load_direct_submit_only_config_and_resolve_relative_skills_dir() {
+    let root = std::env::temp_dir().join(format!("sgclaw-direct-submit-only-config-{}", Uuid::new_v4()));
+    fs::create_dir_all(&root).unwrap();
+    let config_path = root.join("sgclaw_config.json");
+
+    fs::write(
+        &config_path,
+        r#"{
+  "providers": [],
+  "skillsDir": "skill_lib",
+  "directSubmitSkill": "fault-details-report.collect_fault_details"
+}"#,
+    )
+    .unwrap();
+
+    let settings = SgClawSettings::load(Some(config_path.as_path()))
+        .unwrap()
+        .expect("expected sgclaw settings from config file");
+
+    assert_eq!(
+        settings.direct_submit_skill.as_deref(),
+        Some("fault-details-report.collect_fault_details")
+    );
+    assert_eq!(settings.skills_dir, Some(root.join("skill_lib")));
+}
+
+#[test]
+fn sgclaw_settings_reject_invalid_direct_submit_skill_format() {
+    let root = std::env::temp_dir().join(format!(
+        "sgclaw-invalid-direct-submit-skill-{}",
+        Uuid::new_v4()
+    ));
+    fs::create_dir_all(&root).unwrap();
+    let config_path = root.join("sgclaw_config.json");
+
+    fs::write(
+        &config_path,
+        r#"{
+  "providers": [],
+  "skillsDir": "skill_lib",
+  "directSubmitSkill": "fault-details-report"
+}"#,
+    )
+    .unwrap();
+
+    let err = SgClawSettings::load(Some(config_path.as_path()))
+        .expect_err("expected invalid directSubmitSkill format");
+    let message = err.to_string();
+
+    assert!(message.contains("directSubmitSkill"));
+    assert!(message.contains("skill.tool"));
+}
+
 #[test]
 fn sgclaw_settings_load_new_runtime_fields_from_browser_config() {
     let root = std::env::temp_dir().join(format!("sgclaw-runtime-config-{}", Uuid::new_v4()));