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_docker.go

@@ -5,10 +5,11 @@ import (
 	"fmt"
 	"strings"
 
-	"github.com/kballard/go-shellquote"
 	"github.com/nektos/act/pkg/common"
 	"github.com/nektos/act/pkg/container"
 	"github.com/nektos/act/pkg/model"
+
+	"github.com/kballard/go-shellquote"
 )
 
 type stepDocker struct {
@@ -85,11 +86,9 @@ func (sd *stepDocker) runUsesContainer() common.Executor {
 	}
 }
 
-var (
-	ContainerNewContainer = container.NewContainer
-)
+var ContainerNewContainer = container.NewContainer
 
-func (sd *stepDocker) newStepContainer(ctx context.Context, image string, cmd []string, entrypoint []string) container.Container {
+func (sd *stepDocker) newStepContainer(ctx context.Context, image string, cmd, entrypoint []string) container.Container {
 	rc := sd.RunContext
 	step := sd.Step
 
@@ -123,7 +122,7 @@ func (sd *stepDocker) newStepContainer(ctx context.Context, image string, cmd []
 		Name:         createSimpleContainerName(rc.jobContainerName(), "STEP-"+step.ID),
 		Env:          envList,
 		Mounts:       mounts,
-		NetworkMode:  fmt.Sprintf("container:%s", rc.jobContainerName()),
+		NetworkMode:  "container:" + rc.jobContainerName(),
 		Binds:        binds,
 		Stdout:       logWriter,
 		Stderr:       logWriter,