feat(extension): add schema contracts (#3384)

scripts/check_extension_schema_boundaries.sh

@@ -0,0 +1,30 @@
+#!/usr/bin/env bash
+
+set -euo pipefail
+
+ROOT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
+CRATE_DIR="${ROOT_DIR}/crates/extension-schema"
+CARGO_TOML="${CRATE_DIR}/Cargo.toml"
+
+fail() {
+  printf 'Extension schema boundary check failed: %s\n' "$1" >&2
+  exit 1
+}
+
+[[ -f "$CARGO_TOML" ]] || fail "crates/extension-schema/Cargo.toml is missing"
+
+grep -qxF '    "crates/extension-schema", # Extension schema contracts' "${ROOT_DIR}/Cargo.toml" ||
+  fail "workspace members must include crates/extension-schema"
+
+grep -Eq '^rustfs-extension-schema = \{ path = "crates/extension-schema", version = "[^"]+" \}$' "${ROOT_DIR}/Cargo.toml" ||
+  fail "workspace dependencies must include rustfs-extension-schema"
+
+if grep -E '^(rustfs-|tokio|axum|hyper|reqwest|tower|s3s)[A-Za-z0-9_-]*[[:space:]]*=' "$CARGO_TOML" >/dev/null; then
+  fail "extension-schema must stay a lightweight contract crate"
+fi
+
+if (cd "$ROOT_DIR" && rg -n 'rustfs_targets|rustfs_ecstore|rustfs::|tokio::|axum::|hyper::|reqwest::' crates/extension-schema/src >/dev/null); then
+  fail "extension-schema source must not depend on runtime or implementation crates"
+fi
+
+echo "Extension schema boundaries passed."