feat(graph): owner_id 寫入鏈必經(根治無主資料)——配合 base owner-mandatory(D28)

- kbdb-client requireOwner 守衛:漏 owner 插件端即 throw,不再靜默送 owner:''
- owner 一路 thread:persistNodes/ingestEnvelope/entity-crud/triplet-crud 全必填
- 病灶修:POST /triplets/ingest 原本沒傳 owner→加 owner_id query+400
- 寫入 route 缺 owner→400;vitest 23→27
- 註:gloss-bridge 分支的 backfill/gloss-entry 另需套 owner 必填(附說明),不跨支疊改

src/actions/triplet-extract.ts

@@ -55,7 +55,7 @@ export async function extractTripletsViaLLM(ai: Ai, chunks: string[]): Promise<L
 export async function writeTripletToDb(
   client: KbdbClient,
   t: { subject: string; predicate: string; object: string; confidence?: number },
-  owner: string | null,
+  owner: string,  // 必經：萃取寫入必帶 owner（不再收 null → 不會 owner_id: undefined）
 ): Promise<boolean> {
   // 查重：以 S-P-O 三欄精確比對（queryTriplets 取 template record 後在插件層 filter）
   const { count } = await queryTriplets(client, {
@@ -71,7 +71,7 @@ export async function writeTripletToDb(
     predicate: t.predicate,
     object: t.object,
     confidence: t.confidence ?? 0.8,
-    owner_id: owner ?? undefined,
+    owner_id: owner,
   });
   return true;
 }