build: Add post-checkout hook to run bun install

.githooks/post-checkout

@@ -0,0 +1,9 @@
+#!/usr/bin/env bash
+# Post-checkout hook to run bun install when switching branches or checking out files
+# This ensures dependencies are always up to date
+
+# Only run if package.json or bun.lock exist (indicating a Node/Bun project)
+if [ -f "package.json" ] || [ -f "bun.lock" ]; then
+  echo "Running bun install..."
+  bun install
+fi