Add goreleaser config and version command for v0.1.0.

GoReleaser builds static binaries for linux/darwin on amd64/arm64,
injecting version via ldflags. Version command prints the embedded
version (defaults to "dev" for local builds).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.goreleaser.yaml

@@ -0,0 +1,40 @@
+version: 2
+
+before:
+  hooks:
+    - go mod tidy
+
+builds:
+  - main: ./cmd/sgard
+    env:
+      - CGO_ENABLED=0
+    ldflags:
+      - -s -w -X main.version={{.Version}}
+    goos:
+      - linux
+      - darwin
+    goarch:
+      - amd64
+      - arm64
+
+archives:
+  - formats: [binary]
+    name_template: >-
+      {{ .ProjectName }}_{{ .Os }}_{{ .Arch }}{{- if .Arm }}v{{ .Arm }}{{ end }}_v{{ .Version }}
+
+changelog:
+  sort: asc
+  filters:
+    exclude:
+      - "^docs:"
+      - "^test:"
+
+release:
+  github:
+    owner: kisom
+    name: sgard
+  footer: >-
+
+    ---
+
+    Released by [GoReleaser](https://github.com/goreleaser/goreleaser).