feat: add shared git hooks with setup script

Git hooks were only in .git/hooks/ which isn't tracked by git.
Created a shared githooks/ directory so all contributors get
the pre-commit hook that enforces SDLC requirements.

Changes:
- githooks/pre-commit: Pre-commit hook enforcing SDLC (lint, tests, docs)
- scripts/setup-githooks.sh: Script to configure git core.hooksPath
- README.md: Added first-time setup instructions
- AGENTS.md: Updated startup steps and project structure

Users/agents run ./scripts/setup-githooks.sh after cloning to enable hooks.

Reference: docs/SDLC.md

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scripts/setup-githooks.sh

@@ -0,0 +1,43 @@
+#!/usr/bin/env bash
+#
+# KNEL-Football Secure OS - Git Hooks Setup
+# Configures git to use the shared hooks from the githooks/ directory
+#
+# Run this once after cloning the repository:
+#   ./scripts/setup-githooks.sh
+#
+# Copyright (c) 2026 Known Element Enterprises LLC
+# License: GNU Affero General Public License v3.0 only
+
+set -euo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+REPO_ROOT="$(cd "$SCRIPT_DIR/.." && pwd)"
+HOOKS_DIR="$REPO_ROOT/githooks"
+
+echo "Setting up git hooks..."
+echo "Repository: $REPO_ROOT"
+echo "Hooks directory: $HOOKS_DIR"
+
+# Verify hooks directory exists
+if [[ ! -d "$HOOKS_DIR" ]]; then
+    echo "ERROR: githooks/ directory not found"
+    exit 1
+fi
+
+# Make all hooks executable
+chmod +x "$HOOKS_DIR"/*
+
+# Configure git to use the shared hooks directory
+git -C "$REPO_ROOT" config core.hooksPath githooks/
+
+# Verify configuration
+CONFIGURED_PATH=$(git -C "$REPO_ROOT" config --get core.hooksPath)
+echo ""
+echo "Git hooks configured successfully!"
+echo "  core.hooksPath = $CONFIGURED_PATH"
+echo ""
+echo "Available hooks:"
+ls -1 "$HOOKS_DIR"
+echo ""
+echo "Hooks are now active for this repository."