Use golangci-lint fmt to format code (#163)

Use `golangci-lint fmt` to format code, upgrading `.golangci.yml` to v2 and mirroring the linter configuration used by https://github.com/go-gitea/gitea. `gci` now handles import ordering into standard, project-local, blank, and default groups.

Mirrors https://github.com/go-gitea/gitea/pull/37194.

Changes:
- Upgrade `.golangci.yml` to v2 format with the same linter set as gitea (minus `prealloc`, `unparam`, `testifylint`, `nilnil` which produced too many pre-existing issues)
- Add path-based exclusions (`bodyclose`, `gosec` in tests; `gosec:G115`/`G117` globally)
- Run lint via `make lint-go` in CI instead of `golangci/golangci-lint-action`, matching the pattern used by other Gitea repos
- Apply safe auto-fixes (`modernize`, `perfsprint`, `usetesting`, etc.)
- Add explanations to existing `//nolint` directives
- Remove dead code (unused `newRemoteReusableWorkflow` and `networkName`), duplicate imports, and shadowed `max` builtins
- Replace deprecated `docker/distribution/reference` with `distribution/reference`
- Fix `Deprecated:` comment casing and simplify nil/len checks

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

Reviewed-on: https://gitea.com/gitea/act/pulls/163
Reviewed-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: silverwind <me@silverwind.io>
Co-committed-by: silverwind <me@silverwind.io>

pkg/runner/step_run.go

@@ -3,15 +3,16 @@ package runner
 import (
 	"context"
 	"fmt"
+	"maps"
 	"runtime"
 	"strings"
 
-	"github.com/kballard/go-shellquote"
-
 	"github.com/nektos/act/pkg/common"
 	"github.com/nektos/act/pkg/container"
 	"github.com/nektos/act/pkg/lookpath"
 	"github.com/nektos/act/pkg/model"
+
+	"github.com/kballard/go-shellquote"
 )
 
 type stepRun struct {
@@ -90,7 +91,7 @@ func getScriptName(rc *RunContext, step *model.Step) string {
 	for rcs := rc; rcs.Parent != nil; rcs = rcs.Parent {
 		scriptName = fmt.Sprintf("%s-composite-%s", rcs.Parent.CurrentStep, scriptName)
 	}
-	return fmt.Sprintf("workflow/%s", scriptName)
+	return "workflow/" + scriptName
 }
 
 // TODO: Currently we just ignore top level keys, BUT we should return proper error on them
@@ -184,9 +185,7 @@ func (sr *stepRun) setupShell(ctx context.Context) {
 			}
 			step.Shell = shellWithFallback[0]
 			lenv := &localEnv{env: map[string]string{}}
-			for k, v := range sr.env {
-				lenv.env[k] = v
-			}
+			maps.Copy(lenv.env, sr.env)
 			sr.getRunContext().ApplyExtraPath(ctx, &lenv.env)
 			_, err := lookpath.LookPath2(shellWithFallback[0], lenv)
 			if err != nil {
@@ -202,7 +201,7 @@ func (sr *stepRun) setupShell(ctx context.Context) {
 func (sr *stepRun) setupWorkingDirectory(ctx context.Context) {
 	rc := sr.RunContext
 	step := sr.Step
-	workingdirectory := ""
+	var workingdirectory string
 
 	if step.WorkingDirectory == "" {
 		workingdirectory = rc.Run.Job().Defaults.Run.WorkingDirectory