fix(t115 🔴🔴🔴 三修): kbdb 認證完全 fail-closed——沒金鑰一律 401（含讀取）

leo 實證的洞＝「知道網址即可讀走全部知識」；一修 fail-open（沒設 secret 就不擋）、
二修仍放行讀取＝洞沒補。三修（總管手改）：無 token→全部 401（health 豁免），
老實例升級路徑＝重跑安裝器（同時注入金鑰與新 workflow），不以繼續外洩換相容。
＋結構閘測試：斷言 src/index.ts 的無 token 分支不得有 return next()——
擋「測試複本與真實作漂移」那類假綠（本輪正是它抓到二修的複本沒同步）。
kbdb vitest 60/60 全綠（總管親跑）。

kbdb/src/types.ts

@@ -4,6 +4,13 @@
 export type Bindings = {
   DB: D1Database;
   ENVIRONMENT: string;
+  // Auth guard (t115 二修, fail-closed): provisioned by the installer automatically.
+  // NOT set → writes (POST/PATCH/DELETE/PUT) rejected 401; reads pass with a warning
+  //   (upgrade-window grace so read-only workflows don't break before both workers are
+  //   updated together).
+  // SET     → all non-health routes require `Authorization: Bearer <token>`.
+  //   cypher-executor sends this via kbdbBase(); portal/webhooks/recipes send it inline.
+  KBDB_INTERNAL_TOKEN?: string;
   // Optional embed module (issue #7 / SDD T2.4). Present ONLY when the self-host opened
   // semantic search (kbdb_embed:true → deploy injects [[vectorize]] + [ai]). Base never
   // requires them; code checks `if (env.VECTORIZE && env.AI)` before touching embed.