Align step failure log output with GitHub Actions (#927)

Fixes #926.

Before:

<img src="/attachments/a5ae9221-eee2-410a-964e-6103ce126df4" alt="image.png" width="400">

After:

<img width="400" alt="image.png" src="attachments/2f2d67c4-6080-4ec3-9ae5-df33e6479920">

Also gets rid of a bunch of emojis in the logging and the obsolete link to `nektos/act` and align some other error messages.

---
This PR was written with the help of Claude Opus 4.7

---------

Co-authored-by: Nicolas <bircni@icloud.com>
Reviewed-on: https://gitea.com/gitea/runner/pulls/927
Reviewed-by: Nicolas <bircni@icloud.com>
Co-authored-by: silverwind <me@silverwind.io>
Co-committed-by: silverwind <me@silverwind.io>

act/container/host_environment_test.go

@@ -11,6 +11,7 @@ import (
 	"os"
 	"path"
 	"path/filepath"
+	"runtime"
 	"testing"
 
 	"gitea.com/gitea/runner/act/common"
@@ -74,6 +75,31 @@ func TestGetContainerArchive(t *testing.T) {
 	assert.ErrorIs(t, err, io.EOF)
 }
 
+func TestHostEnvironmentExecExitCode(t *testing.T) {
+	if runtime.GOOS == "windows" {
+		t.Skip("uses POSIX shell")
+	}
+	dir := t.TempDir()
+	ctx := context.Background()
+	e := &HostEnvironment{
+		Path:      filepath.Join(dir, "path"),
+		TmpDir:    filepath.Join(dir, "tmp"),
+		ToolCache: filepath.Join(dir, "tool_cache"),
+		ActPath:   filepath.Join(dir, "act_path"),
+		StdOut:    io.Discard,
+		Workdir:   filepath.Join(dir, "path"),
+	}
+	for _, p := range []string{e.Path, e.TmpDir, e.ToolCache, e.ActPath} {
+		assert.NoError(t, os.MkdirAll(p, 0o700)) //nolint:testifylint // test setup
+	}
+
+	err := e.Exec([]string{"sh", "-c", "exit 3"}, map[string]string{"PATH": os.Getenv("PATH")}, "", "")(ctx)
+	var exitErr ExitCodeError
+	require.ErrorAs(t, err, &exitErr)
+	assert.Equal(t, ExitCodeError(3), exitErr)
+	assert.Equal(t, "Process completed with exit code 3.", err.Error())
+}
+
 func TestHostEnvironmentRemoveCleansWorkdir(t *testing.T) {
 	logger := logrus.New()
 	ctx := common.WithLogger(context.Background(), logrus.NewEntry(logger))