ci: add -p=1 to CoverArgs to prevent OOM with race detector

The -coverpkg=./... flag combined with -race instruments all packages in
every test binary, causing excessive memory usage. Serializing test
package execution with -p=1 reduces peak memory to fit within CI runner
limits (Go 1.26 race detector uses more memory than 1.25).

Author: mantzas

.omo/run-continuation/ses_1cf41125affeTuqAftzDwdL4xg.json

@@ -0,0 +1,10 @@
+{
+  "sessionID": "ses_1cf41125affeTuqAftzDwdL4xg",
+  "updatedAt": "2026-05-16T12:41:45.622Z",
+  "sources": {
+    "background-task": {
+      "state": "idle",
+      "updatedAt": "2026-05-16T12:41:45.622Z"
+    }
+  }
+}

targets/test/test.go

@@ -32,6 +32,7 @@ var (
 	CoverArgs = []string{
 		"test",
 		"-mod=vendor",
+		"-p=1",
 		"-coverpkg=./...",
 		"-covermode=atomic",
 		"-coverprofile=coverage.txt",