fix(httpapi): 封存队列作业 id 按 jobs.id 列宽拼短

真实请求 POST /api/v1/library/captures 一律 500：拼出来的
"library-capture-<scope>-<nano>" 是 45 个字符，而 jobs.id 是 varchar(36)，
PG 直接拒绝（value too long）。此前页面一直停在"未接线"，这条路径从没被
真实请求覆盖过，所以只有接上 agent 之后才暴露。

改为 libcap-<scope>-<nano>（35 字符），并用测试锁住列宽与形状。

试过：go test ./internal/httpapi -run LibraryCapture 全绿；修复前用真实
DATABASE_URL 复现 enqueue error: value too long for type character varying(36)。

internal/httpapi/library_capture.go

@@ -97,7 +97,10 @@ func libraryCaptureEnqueue(w http.ResponseWriter, r *http.Request, config Config
 			}
 		}
 	}
-	requestedID := fmt.Sprintf("library-capture-%s-%d", request.Scope, now.UnixNano())
+	// 队列作业 id 落进 jobs.id（varchar(36)）：原来拼 "library-capture-<scope>-<nano>"
+	// 是 45 个字符，真实请求 100% 被 PG 拒（value too long）——只是页面一直停在
+	// "未接线"上，没人走到这里。这里按列宽拼短 id，并留出 scope 全称。
+	requestedID := fmt.Sprintf("libcap-%s-%d", request.Scope, now.UnixNano())
 	// The idempotency key is the capture job id: the same logical capture must map
 	// to one queue row. Binding the scope into the key would silently create a
 	// second job instead of reporting a conflicting request, so the conflict is

internal/httpapi/library_capture_test.go

@@ -86,6 +86,27 @@ func TestLibraryCaptureRejectsInvalidRequest(t *testing.T) {
 	}
 }
 
+func TestLibraryCaptureQueueIDFitsTheColumn(t *testing.T) {
+	// jobs.id 是 varchar(36)：拼长的 id 会在真实 PG 上 500（value too long）。
+	// 页面长期停在"未接线"，这条从没被真实请求覆盖过，所以用测试锁住列宽。
+	for _, scope := range []string{"internal", "external"} {
+		store := &fakeJobStore{enqueueEchoRequestedID: true}
+		recorder := httptest.NewRecorder()
+		libraryCaptureEnqueue(recorder, captureRequest(`{"scope":"`+scope+`"}`),
+			Config{Store: store, LibraryAgentSocket: "/tmp/agent.sock"})
+		if recorder.Code != http.StatusAccepted {
+			t.Fatalf("%s status=%d body=%s", scope, recorder.Code, recorder.Body.String())
+		}
+		enqueued := store.enqueued
+		if len(enqueued.ID) > 36 {
+			t.Fatalf("%s 队列作业 id 超长（%d）：%q", scope, len(enqueued.ID), enqueued.ID)
+		}
+		if !strings.HasPrefix(enqueued.ID, "libcap-"+scope+"-") {
+			t.Fatalf("%s 队列作业 id 形状变了：%q", scope, enqueued.ID)
+		}
+	}
+}
+
 func TestLibraryCaptureJobsAsksStoreForItsOwnType(t *testing.T) {
 	// The global queue is busy with unrelated traffic; the capture job must still
 	// be visible because the query is type-scoped, not filtered after the fact.