Run pre-commit security check as non-root (UID 1001)

docker run was using python:3.12-slim's default root user, causing pip
to warn about running as root. Fix: add -u 1001:1001, set HOME=/tmp so
pip --user has a writable install location, and pass --user to pip.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.githooks/pre-commit

@@ -19,8 +19,10 @@ docker run --rm \
   -v "$REPO_ROOT":/repo \
   -w /repo \
   -e STAGED_FILES="$STAGED" \
+  -u 1001:1001 \
+  -e HOME=/tmp \
   python:3.12-slim \
-  sh -c "pip install --quiet bandit && python scripts/security_check.py"
+  sh -c "pip install --quiet --user bandit && python scripts/security_check.py"
 
 EXIT_CODE=$?