Make script/test fail on flaky failures and enable -race (closes #32)

script/test ended with a verbose rerun whose exit status became the
script's, so a test that failed once and passed on the retry gave a
green build. It now follows the REPO_POLICIES.md pattern: go vet, then
go test -count=1 -timeout 30s -race -cover; on failure a verbose rerun
for the details, then exit 1. -count=1 stays on both go test lines
because the Dockerfile keeps Go's build cache between builds.

The tests that gave the secret binary a minute, and the PGP unlocker
test's 30-second timer, now use 10 seconds, so a hang fails with the
test's own message before the package's 30-second timeout. The README
describes the new run.

Model: opus-5-5

internal/cli/entry_test.go

@@ -8,7 +8,6 @@ import (
 	"path/filepath"
 	"strings"
 	"testing"
-	"time"
 
 	"github.com/awnumar/memguard"
 	"github.com/stretchr/testify/assert"
@@ -52,7 +51,7 @@ func TestInterruptExitsThroughMemguard(t *testing.T) {
 
 	const waitingForValue = "Reading secret value from stdin"
 
-	ctx, cancel := context.WithTimeout(t.Context(), time.Minute)
+	ctx, cancel := context.WithTimeout(t.Context(), commandWait)
 	defer cancel()
 
 	wd, err := filepath.Abs("../..")