Add environment variable for plugin names to the mcp configuration

[keertip]

This PR

• moves the mcp configuration to the plugin.json file for the respective agents
• adds an environment variable to indicate the agent plugin calling the mcp server
• remove the unused .mcp.json file
• bumps the version numbers for the plugins

[gemini-code-assist]

Code Review

This pull request updates the plugin configuration files (.claude-plugin/plugin.json, .codex-plugin/plugin.json, and .cursor-plugin/plugin.json) to bump their versions to 1.0.5 and inline the mcpServers configuration with specific AGENT_PLUGIN environment variables (claude-code, codex, and cursor respectively), while removing the external .mcp.json file. The feedback suggests adding a trailing newline to the end of each of these JSON files to ensure POSIX compatibility and prevent git diff warnings.