Note global-state mutation in three new internal-package test files

The summarizer- and validators-side internal tests added on this branch
swap the package-level log variable (and, for the summarizer handler
test, the summarizerLagEpochs gauge) and restore the originals on
teardown.  Add a top-of-file note in each file warning future
contributors not to add t.Parallel() to any test here, since the global
mutation would race across goroutines.

No behavioural change.

Author: AntiD2ta

services/summarizer/standard/handler_internal_test.go

@@ -27,6 +27,11 @@ import (
 	"github.com/wealdtech/chaind/services/chaindb"
 )
 
+// Tests in this file mutate package-level state — the unexported `log` variable
+// and the `summarizerLagEpochs` gauge — and restore the originals on teardown.
+// Do NOT add t.Parallel() to any test here; the global mutation would race
+// across goroutines.
+
 // stubValidatorsProvider drives summarizeEpoch into the silent-skip and
 // zero-balance branches.
 type stubValidatorsProvider struct {

services/summarizer/standard/validatorday_internal_test.go

@@ -27,6 +27,10 @@ import (
 	mockchaintime "github.com/wealdtech/chaind/services/chaintime/mock"
 )
 
+// Tests in this file mutate the package-level `log` variable and restore it on
+// teardown.  Do NOT add t.Parallel() to any test here — the global mutation
+// would race across goroutines.
+
 // stubBalanceChainDB pops balance responses from a queue so one fixture can
 // drive both the start-balances and end-balances guard paths.  daySummariesSet
 // records writes so tests can assert the guard short-circuits.

services/validators/standard/handler_internal_test.go

@@ -29,6 +29,10 @@ import (
 	"github.com/wealdtech/chaind/services/chaindb"
 )
 
+// Tests in this file mutate the package-level `log` variable via captureWarnLog
+// and restore it on teardown.  Do NOT add t.Parallel() to any test here — the
+// global mutation would race across goroutines.
+
 // captureWarnLog redirects the package logger to a byte buffer at WarnLevel
 // and returns the buffer plus a restore func.
 func captureWarnLog(t *testing.T) (*bytes.Buffer, func()) {