fix: eliminate all 4xx noise from scene walks

- buildScenarios: drop the /api/runtime/transactions/{id} headline GET
  entirely. Synthesize the RuntimeTransaction shape from the work-item
  data. Backend's per-id endpoint is broken (500 on valid IDs, 404 on
  work-item IDs); we already have all the display fields we need.
- store.ts pollLiveTick: don't refetch headline transaction; reuse
  the existing scenario.raw.headlineRt synthesized at build time.
- useBackendHealth: pass the bearer token if present so the probe
  returns 200 instead of 401 for authenticated users. The probe still
  treats 401 as 'up' for unauthenticated landing page.
- agentMemory.remember: track ensureVault result. Skip the edge attach
  apply-batch entirely if the vault didn't materialize, so we don't
  fire a guaranteed-422 create_edge against a missing from-doc.

src/lib/agentMemory.ts

@@ -66,7 +66,7 @@ export const agentMemory = {
   async remember(email: string, content: string, tags: string[] = [], signal?: AbortSignal): Promise<string | null> {
     if (!content.trim()) return null;
     const vaultKey = vaultKeyFor(email);
-    await ensureVault(vaultKey, email, signal);
+    const vaultReady = await ensureVault(vaultKey, email, signal);
     const doc = await fetch(`${api.config.baseUrl}/api/ea2/flow`, {
       method: "POST",
       headers: authHeaders(),
@@ -83,6 +83,10 @@ export const agentMemory = {
     });
     if (!doc.ok) return null;
     const mem = await doc.json();
+    if (!vaultReady) {
+      console.warn(`[memory] vault not ready for ${email}, skipping edge attach`);
+      return mem._key;
+    }
     try {
       const edgeRes = await fetch(`${api.config.baseUrl}/api/ea2/apply-batch`, {
         method: "POST",