feat: add one-command plugin installer (make install-plugin)

**Problem:**
- Old installation method required manual file copying or complex marketplace setup
- Users had to run `/plugin marketplace add` + `/plugin install` (tedious)
- No automated installation workflow

**Solution:**
- Add `make install-plugin` for one-command installation
- Copies `.claude-plugin/` to `~/.claude/plugins/pm-agent/`
- Add `make uninstall-plugin` and `make reinstall-plugin`
- Update README.md with clear installation instructions

**Changes:**

Makefile:
- Add install-plugin target: Copy plugin to ~/.claude/plugins/
- Add uninstall-plugin target: Remove plugin
- Add reinstall-plugin target: Update existing installation
- Update help menu with plugin management section

README.md:
- Replace complex marketplace instructions with `make install-plugin`
- Add plugin management commands section
- Update troubleshooting guide
- Simplify migration guide from v1.x

**Installation Flow:**
```bash
git clone https://github.com/SuperClaude-Org/SuperClaude_Framework.git
cd SuperClaude_Framework
make install-plugin
# Restart Claude Code → Plugin auto-activates
```

**Features:**
- One-command install (no manual config)
- Auto-activation via SessionStart hook
- Hot reload support (TypeScript)
- Clean uninstall/reinstall workflow

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

Makefile

@@ -1,4 +1,4 @@
-.PHONY: dev install test test-plugin doctor verify clean lint format help
+.PHONY: dev install test test-plugin doctor verify clean lint format install-plugin uninstall-plugin reinstall-plugin help
 
 # Development installation (local source, editable) - RECOMMENDED
 dev:
@@ -64,6 +64,46 @@ clean:
 	find . -type d -name .pytest_cache -exec rm -rf {} +
 	find . -type d -name .ruff_cache -exec rm -rf {} +
 
+# Install Claude Code plugin
+install-plugin:
+	@echo "🔌 Installing SuperClaude plugin to Claude Code..."
+	@if [ -d ~/.claude/plugins/pm-agent ]; then \
+		echo "⚠️  Plugin already exists at ~/.claude/plugins/pm-agent"; \
+		echo "   Run 'make reinstall-plugin' to update"; \
+		exit 1; \
+	fi
+	@mkdir -p ~/.claude/plugins/pm-agent
+	@cp -r .claude-plugin/* ~/.claude/plugins/pm-agent/
+	@echo ""
+	@echo "✅ Plugin installed successfully!"
+	@echo ""
+	@echo "📋 Installed components:"
+	@echo "   - PM Agent: Auto-activation orchestrator (SessionStart hook)"
+	@echo "   - Research: Deep web search with adaptive planning"
+	@echo "   - Index: Repository indexing (94% token reduction)"
+	@echo ""
+	@echo "🔄 Restart Claude Code or run /plugin to verify installation"
+	@echo "   Available commands: /pm, /research, /index-repo"
+
+# Uninstall Claude Code plugin
+uninstall-plugin:
+	@echo "🗑️  Uninstalling SuperClaude plugin..."
+	@if [ ! -d ~/.claude/plugins/pm-agent ]; then \
+		echo "❌ Plugin not found at ~/.claude/plugins/pm-agent"; \
+		exit 1; \
+	fi
+	@rm -rf ~/.claude/plugins/pm-agent
+	@echo "✅ Plugin uninstalled successfully"
+
+# Reinstall Claude Code plugin (uninstall + install)
+reinstall-plugin:
+	@echo "🔄 Reinstalling SuperClaude plugin..."
+	@rm -rf ~/.claude/plugins/pm-agent 2>/dev/null || true
+	@mkdir -p ~/.claude/plugins/pm-agent
+	@cp -r .claude-plugin/* ~/.claude/plugins/pm-agent/
+	@echo "✅ Plugin reinstalled successfully"
+	@echo "🔄 Restart Claude Code to apply changes"
+
 # Translate README to multiple languages using Neural CLI
 translate:
 	@echo "🌐 Translating README using Neural CLI (Ollama + qwen2.5:3b)..."
@@ -90,6 +130,7 @@ help:
 	@echo "🚀 Quick Start:"
 	@echo "  make dev             - Install in development mode (RECOMMENDED)"
 	@echo "  make verify          - Verify installation is working"
+	@echo "  make install-plugin  - Install plugin to Claude Code (~/.claude/plugins/)"
 	@echo ""
 	@echo "🔧 Development:"
 	@echo "  make test            - Run test suite"
@@ -99,6 +140,11 @@ help:
 	@echo "  make format          - Format code (ruff format)"
 	@echo "  make clean           - Clean build artifacts"
 	@echo ""
+	@echo "🔌 Plugin Management:"
+	@echo "  make install-plugin  - Install plugin to Claude Code"
+	@echo "  make uninstall-plugin - Remove plugin from Claude Code"
+	@echo "  make reinstall-plugin - Update existing plugin installation"
+	@echo ""
 	@echo "📚 Documentation:"
 	@echo "  make translate       - Translate README to Chinese and Japanese"
 	@echo "  make help            - Show this help message"