Document project, add AGENTS.md release workflow and release script

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

scripts/release.sh

@@ -0,0 +1,35 @@
+#!/usr/bin/env bash
+# Bump VERSION, build, run the e2e suite, commit everything, tag.
+# Usage: scripts/release.sh patch|minor|major "commit subject"
+# Refuses to run when the build or tests fail. Does not push.
+set -euo pipefail
+cd "$(dirname "$0")/.."
+
+kind=${1:?usage: release.sh patch|minor|major "subject"}
+subject=${2:?usage: release.sh patch|minor|major "subject"}
+
+IFS=. read -r maj min pat < VERSION
+case "$kind" in
+  patch) pat=$((pat+1)) ;;
+  minor) min=$((min+1)); pat=0 ;;
+  major) maj=$((maj+1)); min=0; pat=0 ;;
+  *) echo "kind must be patch, minor or major" >&2; exit 2 ;;
+esac
+new="$maj.$min.$pat"
+
+if git rev-parse "v$new" >/dev/null 2>&1; then echo "tag v$new already exists" >&2; exit 1; fi
+if grep -rl $'\xe2\x80\x94' --exclude-dir=build --exclude-dir=.git . | grep -q .; then
+  echo "em dash found, remove it first" >&2; exit 1
+fi
+
+echo "$new" > VERSION
+cmake -S . -B build >/dev/null
+cmake --build build
+tests/run.sh
+
+git add -A
+git commit -m "$subject
+
+Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>"
+git tag -a "v$new" -m "doos $new"
+echo "released v$new"