docs: add Headlamp plugin installation guides and setup script

Add comprehensive installation documentation and automated setup for
Headlamp plugin manager integration.

New files:
- install-plugin.sh: Automated installation script for macOS/Linux
- HEADLAMP_INSTALLATION.md: Complete installation guide covering:
  - Local installation (development/testing)
  - NPM installation (for published plugin)
  - Headlamp server mode
  - Kubernetes deployment with ConfigMaps
  - Troubleshooting common issues
  - Uninstallation instructions
- SETUP_STATUS.md: Quick reference for current setup status

Features:
- Cross-platform support (macOS, Linux, Windows)
- Multiple installation methods documented
- Troubleshooting guide for common issues
- Development mode instructions
- Plugin verification steps

Plugin is now ready for:
✅ Local Headlamp desktop installation
✅ Headlamp server deployment
✅ Kubernetes-based Headlamp with ConfigMaps
✅ Development with hot reload

Current installation:
- Location: ~/Library/Application Support/Headlamp/plugins/headlamp-sealed-secrets/
- Version: 0.2.0
- Sealed Secrets controller: Running in cluster
- Status: Ready for use

Generated with [Claude Code](https://claude.ai/code)
via [Happy](https://happy.engineering)

Co-Authored-By: Claude <noreply@anthropic.com>
Co-Authored-By: Happy <yesreply@happy.engineering>

install-plugin.sh

@@ -0,0 +1,79 @@
+#!/bin/bash
+#
+# Install Headlamp Sealed Secrets Plugin
+#
+# This script builds and installs the plugin to your local Headlamp installation.
+#
+
+set -e
+
+# Colors for output
+RED='\033[0;31m'
+GREEN='\033[0;32m'
+YELLOW='\033[1;33m'
+NC='\033[0m' # No Color
+
+echo -e "${GREEN}Headlamp Sealed Secrets Plugin Installer${NC}"
+echo "=========================================="
+echo
+
+# Detect OS and set plugin directory
+if [[ "$OSTYPE" == "darwin"* ]]; then
+    PLUGIN_DIR="$HOME/Library/Application Support/Headlamp/plugins/headlamp-sealed-secrets"
+    echo -e "${YELLOW}Detected: macOS${NC}"
+elif [[ "$OSTYPE" == "linux-gnu"* ]]; then
+    PLUGIN_DIR="$HOME/.config/Headlamp/plugins/headlamp-sealed-secrets"
+    echo -e "${YELLOW}Detected: Linux${NC}"
+else
+    echo -e "${RED}Unsupported OS: $OSTYPE${NC}"
+    echo "For Windows, please see HEADLAMP_INSTALLATION.md"
+    exit 1
+fi
+
+echo "Plugin will be installed to: $PLUGIN_DIR"
+echo
+
+# Check if node/npm are available
+if ! command -v npm &> /dev/null; then
+    echo -e "${RED}Error: npm is not installed${NC}"
+    echo "Please install Node.js and npm first"
+    exit 1
+fi
+
+# Navigate to plugin directory
+cd "$(dirname "$0")/headlamp-sealed-secrets"
+
+echo -e "${GREEN}Step 1: Installing dependencies...${NC}"
+npm install
+
+echo
+echo -e "${GREEN}Step 2: Building plugin...${NC}"
+npm run build
+
+echo
+echo -e "${GREEN}Step 3: Creating plugin directory...${NC}"
+mkdir -p "$PLUGIN_DIR"
+
+echo
+echo -e "${GREEN}Step 4: Copying plugin files...${NC}"
+cp -v dist/main.js "$PLUGIN_DIR/"
+cp -v package.json "$PLUGIN_DIR/"
+cp -v README.md "$PLUGIN_DIR/" 2>/dev/null || true
+cp -v LICENSE "$PLUGIN_DIR/" 2>/dev/null || true
+
+echo
+echo -e "${GREEN}✓ Installation complete!${NC}"
+echo
+echo "Plugin installed to: $PLUGIN_DIR"
+echo
+echo "Next steps:"
+echo "1. Restart Headlamp desktop application"
+echo "2. Open Headlamp and connect to your cluster"
+echo "3. Look for 'Sealed Secrets' in the sidebar"
+echo
+echo "To verify sealed-secrets controller is installed:"
+echo "  kubectl get pods -n kube-system -l name=sealed-secrets-controller"
+echo
+echo "To install sealed-secrets controller (if not present):"
+echo "  kubectl apply -f https://github.com/bitnami-labs/sealed-secrets/releases/download/v0.24.0/controller.yaml"
+echo