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/container/linux_container_environment_extensions_test.go

@@ -31,22 +31,17 @@ func TestContainerPath(t *testing.T) {
 		for _, v := range []containerPathJob{
 			{"/mnt/c/Users/act/go/src/github.com/nektos/act", "C:\\Users\\act\\go\\src\\github.com\\nektos\\act\\", ""},
 			{"/mnt/f/work/dir", `F:\work\dir`, ""},
-			{"/mnt/c/windows/to/unix", "windows\\to\\unix", fmt.Sprintf("%s\\", rootDrive)},
-			{fmt.Sprintf("/mnt/%v/act", rootDriveLetter), "act", fmt.Sprintf("%s\\", rootDrive)},
+			{"/mnt/c/windows/to/unix", "windows\\to\\unix", rootDrive + "\\"},
+			{fmt.Sprintf("/mnt/%v/act", rootDriveLetter), "act", rootDrive + "\\"},
 		} {
 			if v.workDir != "" {
-				if err := os.Chdir(v.workDir); err != nil {
-					log.Error(err)
-					t.Fail()
-				}
+				t.Chdir(v.workDir)
 			}
 
 			assert.Equal(t, v.destinationPath, linuxcontainerext.ToContainerPath(v.sourcePath))
 		}
 
-		if err := os.Chdir(cwd); err != nil {
-			log.Error(err)
-		}
+		t.Chdir(cwd)
 	} else {
 		cwd, err := os.Getwd()
 		if err != nil {