Add tools command for direct binary downloads from GitHub releases

Introduces a new 'tools' command that installs development tools (golangci-lint, gotestsum)
by downloading pre-built binaries directly from GitHub releases instead of using 'go get -tool'.
This prevents modifications to plugin go.mod files and improves build reliability.

Features:
- Cross-platform support (Windows, macOS, Linux) with automatic architecture detection
- Version-specific binary naming with symlinks for easy access
- Configurable installation directory via --bin-dir flag
- Tar.gz archive extraction with binary validation
- Updated Makefile integration to use downloaded binaries

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

go.mod

@@ -156,6 +156,7 @@ require (
 	github.com/digitorus/timestamp v0.0.0-20231217203849-220c5c2851b7 // indirect
 	github.com/dimchansky/utfbom v1.1.1 // indirect
 	github.com/distribution/reference v0.6.0 // indirect
+	github.com/dnephin/pflag v1.0.7 // indirect
 	github.com/docker/cli v28.1.1+incompatible // indirect
 	github.com/docker/distribution v2.8.3+incompatible // indirect
 	github.com/docker/docker v28.1.1+incompatible // indirect
@@ -239,6 +240,7 @@ require (
 	github.com/google/rpmpack v0.7.0 // indirect
 	github.com/google/s2a-go v0.1.9 // indirect
 	github.com/google/safetext v0.0.0-20240722112252-5a72de7e7962 // indirect
+	github.com/google/shlex v0.0.0-20191202100458-e7afc7fbc510 // indirect
 	github.com/google/uuid v1.6.0 // indirect
 	github.com/google/wire v0.6.0 // indirect
 	github.com/googleapis/enterprise-certificate-proxy v0.3.6 // indirect
@@ -288,6 +290,7 @@ require (
 	github.com/jingyugao/rowserrcheck v1.1.1 // indirect
 	github.com/jjti/go-spancheck v0.6.2 // indirect
 	github.com/jmespath/go-jmespath v0.4.1-0.20220621161143-b0104c826a24 // indirect
+	github.com/jonboulle/clockwork v0.5.0 // indirect
 	github.com/josharian/intern v1.0.0 // indirect
 	github.com/julz/importas v0.1.0 // indirect
 	github.com/karamaru-alpha/copyloopvar v1.1.0 // indirect
@@ -498,6 +501,7 @@ require (
 	gopkg.in/warnings.v0 v0.1.2 // indirect
 	gopkg.in/yaml.v2 v2.4.0 // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect
+	gotest.tools/gotestsum v1.7.0 // indirect
 	honnef.co/go/tools v0.5.1 // indirect
 	k8s.io/klog/v2 v2.130.1 // indirect
 	lukechampine.com/blake3 v1.2.1 // indirect
@@ -512,4 +516,5 @@ tool (
 	github.com/golangci/golangci-lint/cmd/golangci-lint
 	github.com/goreleaser/goreleaser/v2
 	github.com/securego/gosec/v2/cmd/gosec
+	gotest.tools/gotestsum
 )