chore: add semantic versioning and automatic changelog generation

- Add cliff.toml config for git-cliff with conventional commit parsing
- Create scripts/release.sh for automated version bumping
- Generate CHANGELOG.md from git history with semver tags (v1.0.0, v1.7.2)
- Release workflow: ./scripts/release.sh {major|minor|patch|VERSION}

scripts/release.sh

@@ -0,0 +1,51 @@
+#!/usr/bin/env bash
+#
+# Release script: bump version, generate changelog, commit, and tag.
+#
+# Usage:
+#   ./scripts/release.sh <major|minor|patch>
+#   ./scripts/release.sh 2.0.0          # explicit version
+#
+set -euo pipefail
+
+VERSION_FILE="version"
+
+current_version=$(cat "$VERSION_FILE")
+echo "Current version: $current_version"
+
+IFS='.' read -r major minor patch <<< "$current_version"
+
+case "${1:-}" in
+    major) new_version="$((major + 1)).0.0" ;;
+    minor) new_version="${major}.$((minor + 1)).0" ;;
+    patch) new_version="${major}.${minor}.$((patch + 1))" ;;
+    "")
+        echo "Usage: $0 <major|minor|patch|VERSION>"
+        exit 1
+        ;;
+    *)
+        # Validate explicit semver
+        if [[ ! "$1" =~ ^[0-9]+\.[0-9]+\.[0-9]+$ ]]; then
+            echo "Error: '$1' is not a valid semver (X.Y.Z)"
+            exit 1
+        fi
+        new_version="$1"
+        ;;
+esac
+
+echo "Bumping to: $new_version"
+
+# Update version file
+echo "$new_version" > "$VERSION_FILE"
+
+# Generate changelog
+git-cliff --tag "v${new_version}" --output CHANGELOG.md
+
+# Commit and tag
+git add "$VERSION_FILE" CHANGELOG.md
+git commit -m "chore(release): v${new_version}"
+git tag "v${new_version}"
+
+echo ""
+echo "Released v${new_version}"
+echo "Don't forget to push: git push && git push --tags"