fix(skills+memory): builtin handler fallback in executor, skip vector upsert for deleted memories

- skills: Next.js compiles SkillExecutor into multiple chunks (own singleton
  each); route chunk lacked builtin handlers registered at startup via
  instrumentation. execute() now falls back to builtinSkills registry, so
  POST /api/skills/executions works for file_read/web_fetch/etc.
- memory: scheduleVectorUpsert is fire-and-forget and embeddings are slow;
  health-check verify (create->delete test memory) left queued upserts
  failing with 'memory not found' every 30s. Check existence before embedding
  and skip quietly.

src/lib/memory/store.ts

@@ -122,6 +122,17 @@ function safeMarkNeedsReindex(id: string, needs: boolean): void {
 function scheduleVectorUpsert(id: string, content: string): void {
   setImmediate(async () => {
     try {
+      // The upsert is fire-and-forget and embeddings are slow (potion loads
+      // lazily). Health-check verification (and user deletes) can remove the
+      // memory before this callback runs — skip quietly instead of spamming
+      // "memory not found" warnings every sweep interval.
+      const db = getDbInstance();
+      const exists = db.prepare("SELECT rowid FROM memories WHERE id = ?").get(id);
+      if (!exists) {
+        log.debug("memory.vec.upsert.skipped_deleted", { id });
+        return;
+      }
+
       const settings = await getMemorySettings();
       const resolution = resolveEmbeddingSource(settings);
       if (!resolution.source) return;

src/lib/skills/executor.ts

@@ -1,5 +1,6 @@
 import { skillRegistry } from "./registry";
 import { SkillExecution, SkillStatus, SkillHandler } from "./types";
+import { builtinSkills } from "./builtins";
 import { getDbInstance } from "../db/core";
 import { getSettings } from "../db/settings";
 import { randomUUID } from "crypto";
@@ -73,7 +74,19 @@ class SkillExecutor {
         new Date().toISOString()
       );
 
-      const handler = this.handlers.get(skill.handler);
+      let handler = this.handlers.get(skill.handler);
+      if (!handler) {
+        // Builtin handlers are registered by instrumentation-node at startup,
+        // but Next.js may compile this module into multiple chunks (each with
+        // its own SkillExecutor singleton). Fall back to the builtin registry
+        // so `POST /api/skills/executions` works regardless of which chunk the
+        // route is served from.
+        const builtin = builtinSkills[skill.handler];
+        if (builtin) {
+          this.handlers.set(skill.handler, builtin);
+          handler = builtin;
+        }
+      }
       if (!handler) {
         throw new Error(`Handler not found: ${skill.handler}`);
       }