feat(install): add installation script

Introduce install.sh script to build optimized grokkit binary from Go source, install it to ~/.local/bin, and provide usage instructions for setup and PATH configuration.

install.sh

@@ -0,0 +1,27 @@
+#!/bin/bash
+# grokkit - Personal Grok CLI install script
+# Run with: bash install.sh
+
+set -e
+
+echo "🔨 Building optimized grokkit binary..."
+
+go build -ldflags "-s -w" -trimpath -o build/grokkit .
+
+echo "📦 Installing to ~/.local/bin/grokkit..."
+
+mkdir -p ~/.local/bin
+cp build/grokkit ~/.local/bin/grokkit
+chmod +x ~/.local/bin/grokkit
+
+echo "✅ Success! grokkit is now installed."
+echo ""
+echo "You can now run it from anywhere with:"
+echo "   grokkit --help"
+echo ""
+echo "If the command is not found, add this line to your ~/.zshrc (or ~/.bashrc):"
+echo "   export PATH=\"\$HOME/bin:\$PATH\""
+echo ""
+echo "Then run: source ~/.zshrc"
+echo ""
+echo "Enjoy your new Grok superpower! 🚀"