Add project standards files and scripts for consistency

.githooks/README.md

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+# Git Hooks
+
+This repository standard uses a project-local hooks directory:
+
+- `.githooks/pre-commit`
+
+Activate it once per repository:
+
+```sh
+git config core.hooksPath .githooks
+```
+
+The pre-commit hook validates for staged `.sh` files:
+
+- executable bit in Git index (`100755`)
+- LF line endings (no CRLF)

.githooks/pre-commit

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+#!/usr/bin/env sh
+set -eu
+
+failed=0
+cr=$(printf '\r')
+
+staged_shell_files=$(git diff --cached --name-only --diff-filter=ACMR | grep -E '\.sh$' || true)
+
+for file in $staged_shell_files; do
+  mode=$(git ls-files --stage -- "$file" | awk '{print $1}')
+  if [ "$mode" != "100755" ]; then
+    echo "ERROR: $file is not executable in Git index. Run: git add --chmod=+x $file" >&2
+    failed=1
+  fi
+
+  if git show ":$file" | grep -q "$cr"; then
+    echo "ERROR: $file contains CRLF in staged content. Use LF line endings." >&2
+    failed=1
+  fi
+done
+
+if [ "$failed" -ne 0 ]; then
+  echo "Pre-commit check failed." >&2
+  exit 1
+fi