fix(heartbeat,skills): 健康快照降级处理 + 技能加载重试

P1-3: health_snapshot 在 heartbeat engine 未初始化时不再报错，
返回 pending 状态快照，避免 HealthPanel 竞态报错。

P1-1: loadSkillsCatalog 新增 Path C 延迟重试（最多2次，间隔
1.5s/3s），解决 kernel 初始化未完成时 skills 返回空数组的问题。

desktop/src-tauri/src/intelligence/health_snapshot.rs

@@ -47,9 +47,30 @@ pub async fn health_snapshot(
 ) -> Result<HealthSnapshot, String> {
     let engines = heartbeat_state.lock().await;
 
-    let engine = engines
-        .get(&agent_id)
-        .ok_or_else(|| format!("Heartbeat engine not initialized for agent: {}", agent_id))?;
+    // If heartbeat engine not yet initialized, return a graceful "pending" snapshot
+    // instead of erroring — this avoids race conditions when HealthPanel mounts
+    // before the heartbeat bootstrap sequence completes.
+    let engine = match engines.get(&agent_id) {
+        Some(e) => e,
+        None => {
+            tracing::debug!("[health_snapshot] Engine not initialized for {}, returning pending snapshot", agent_id);
+            return Ok(HealthSnapshot {
+                timestamp: chrono::Utc::now().to_rfc3339(),
+                intelligence: IntelligenceHealth {
+                    engine_running: false,
+                    config: HeartbeatConfig::default(),
+                    last_tick: None,
+                    alert_count_24h: 0,
+                    total_checks: 5,
+                },
+                memory: MemoryHealth {
+                    total_entries: 0,
+                    storage_size_bytes: 0,
+                    last_extraction: None,
+                },
+            });
+        }
+    };
 
     let engine_running = engine.is_running().await;
     let config = engine.get_config().await;