build: gate pre-commit hook install behind INSTALL_PRECOMMIT

Port the scripts/make changes from coreai-opt#497 so INSTALL_PRECOMMIT
is a real knob: setup_env.sh defaults it (false in --ensure mode, true
otherwise) and threads it to install_pre_commit_hooks.sh, which skips
`pre-commit install -f` when INSTALL_PRECOMMIT=false.

Author: guru-desh

scripts/make/install_pre_commit_hooks.sh

@@ -60,5 +60,9 @@ if ! command -v lychee &>/dev/null; then
 fi
 
 # Configure git hooks. Force-install so the shebang points to the current venv.
-uv run --no-sync --active pre-commit install -f
-echo "✓ Pre-commit hooks configured to use $VIRTUAL_ENV"
+if [[ "${INSTALL_PRECOMMIT:-true}" == "false" ]]; then
+    echo "Skipping git hook configuration (INSTALL_PRECOMMIT=$INSTALL_PRECOMMIT)"
+else
+    uv run --no-sync --active pre-commit install -f
+    echo "✓ Pre-commit hooks configured to use $VIRTUAL_ENV"
+fi

scripts/make/setup_env.sh

@@ -195,6 +195,12 @@ while [[ $# -gt 0 ]]; do
     esac
 done
 
+if [[ "$ENSURE_MODE" == true ]]; then
+    INSTALL_PRECOMMIT="${INSTALL_PRECOMMIT:-false}"
+else
+    INSTALL_PRECOMMIT="${INSTALL_PRECOMMIT:-true}"
+fi
+
 # Validate required arguments
 if [[ -z "$PYTHON_VERSION" ]]; then
     echo "Error: --python-version is required"
@@ -339,11 +345,11 @@ echo "Running: ${SYNC_CMD[*]}"
 "${SYNC_CMD[@]}"
 
 echo ""
-echo "[3/3] Configuring pre-commit hooks..."
+echo "[3/3] Installing hook dependencies and configuring pre-commit hooks..."
 if [[ "$VENV_PREEXISTED" == "true" ]]; then
     echo "Skipped (venv already exists, hooks already configured)"
 else
-    "$SCRIPTS_DIR/make/install_pre_commit_hooks.sh" "$COREAI_OPT_HOME"
+    INSTALL_PRECOMMIT="$INSTALL_PRECOMMIT" "$SCRIPTS_DIR/make/install_pre_commit_hooks.sh" "$COREAI_OPT_HOME"
 fi
 
 echo ""