Add Claude Code plugin support

[amondnet]

Description

Add Claude Code plugin support to enable easy installation and use of Neo4j MCP servers through the Claude Code plugin system.

This PR adds a .claude-plugin/plugin.json manifest file that configures all four MCP servers (Cypher, Memory, Aura API, Data Modeling) to work seamlessly with Claude Code's plugin system.

Installation

Users can install this plugin via the pleaseai marketplace:

# Add the pleaseai marketplace
/plugin marketplace add pleaseai/claude-code-plugins

# Install the mcp-neo4j plugin
/plugin install mcp-neo4j@pleaseai

Type of Change

• New feature
• Bug fix
• Breaking change
• Documentation update
• Project configuration change

Complexity

• LOW
• MEDIUM
• HIGH

This is a low-complexity change that only adds a new configuration file without modifying any existing code or functionality.

How Has This Been Tested?

• Unit tests
• Integration tests
• Manual tests

Manual testing performed:

• Verified plugin.json follows Claude Code plugin specification
• Confirmed all four MCP servers are correctly configured
• Validated JSON syntax and structure

Checklist

• Documentation has been updated (added plugin.json)
• Unit tests have been updated (N/A - configuration only)
• Integration tests have been updated (N/A - configuration only)
• Server has been tested in an MCP application (to be tested after merge)
• CHANGELOG.md updated if appropriate (can be added if needed)