build: add preflight validator family for versions/manifest/changelog drift

Establishes the local pre-push gate. preflight.sh runs four blocks: version
consistency, manifest shape (Icon plus all ImageUrls), changelog sync, plus a
release build as compile-health smoke. setup-hooks.sh wires core.hooksPath to
.githooks. .gitignore opens scripts/ for tracking (setup-dev-env.sh stays
private). Test execution itself lives in a separate local repository and is
not part of this codebase.

scripts/setup-hooks.sh

@@ -0,0 +1,13 @@
+#!/usr/bin/env bash
+# setup-hooks.sh — installs pre-push hook via core.hooksPath. Idempotent.
+# Note: NO pre-commit hook — test execution is local-only in the Build-Suite repo,
+# so the plugin repo's pre-commit cannot run tests. Versions/manifest/changelog
+# checks happen on pre-push only.
+
+set -euo pipefail
+ROOT="$(cd "$(dirname "$0")/.." && pwd)"
+cd "$ROOT"
+
+git config core.hooksPath .githooks
+chmod +x .githooks/pre-push
+echo "setup-hooks: core.hooksPath set to .githooks. pre-push live."