feat: add version command and improve --version output

[Copilot]

Adapts the feature from score-compose#467 to score-radius: improves --version output and adds a new version subcommand.

Changes

• internal/version/version.go: Drop debug.ReadBuildInfo in favour of build-time ldflags; add GitCommit and BuildDate vars. New format:

  score-radius 0.1.0 (go1.26.2 - linux/amd64)
  git commit: abc123def
  build date: 2026-04-16T00:00:00Z
  

• internal/command/root.go: Introduce ScoreImplementationName constant; set a custom cobra version template (removes the default version word from output).
• internal/command/version.go: New score-radius version subcommand — prints Score ASCII logo, version info, and checks GitHub releases for a newer version. Flags: --no-logo, --no-updates-check.
• .goreleaser.yaml: Inject GitCommit and BuildDate via ldflags at release build time.
• Dockerfile: Accept GIT_COMMIT/BUILD_DATE build ARGs and pass them as ldflags so container image builds report accurate metadata (previously showed build: local, sha: unknown).
• .github/workflows/release.yaml: Forward GIT_COMMIT and BUILD_DATE as Docker build-args.
• root_test.go: Add TestRootVersion asserting the new output format.

[github-actions]

Overview

Image reference	score-radius:latest	score-radius:latest
- digest	4a25b647910f	80ddc1796b7d
- tag	latest	latest
- provenance	ec5e0f2	ae3ef98
- vulnerabilities
- platform	linux/amd64	linux/amd64
- size	5.4 MB	5.4 MB (-3.7 kB)
- packages	40	40

Policies (0 improved, 0 worsened)

Policy Name	score-radius:latest	score-radius:latest	Change	Standing
Default non-root user	✅	✅		No Change
No AGPL v3 licenses	✅	✅		No Change
No fixable critical or high vulnerabilities	✅	✅		No Change
No high-profile vulnerabilities	✅	✅		No Change
No outdated base images	✅	✅		No Change
No unapproved base images	✅	✅		No Change
Supply chain attestations	✅	✅		No Change
Valid Docker Hardened Image (DHI) or DHI base image	⚠️ 2	⚠️ 2		No Change

Packages and Vulnerabilities (1 package changes and 0 vulnerability changes)

• ♾️ 1 packages changed
• 39 packages unchanged

Changes for packages of type golang (1 changes)

	Package	Version score-radius:latest	Version score-radius:latest
♾️	github.com/score-spec/score-radius	0.0.0-20260412231134-ec5e0f27c33f+dirty	0.0.12-0.20260416012536-ae3ef98ad1ab+dirty

[mathieu-benoit]

LGTM

[mathieu-benoit]

FYI: docs now updated #73