feat: configurable tool group selection

[meirk-brd]

Summary

• add reusable tool group catalog and allowlist builder for the STDIO MCP server
• gate tool registration by PRO_MODE, optional group selections, or explicit tool picks
• surface the new configuration knobs in package metadata and README (using GROUPS/TOOLS in docs)

File Highlights

• tool_groups.js: defines curated bundles, base tools, and helper utilities
• server.js: parses env vars, builds the allowlist, and updates addTool priority flow
• package.json: ships the new module with the published package
• server.json: documents the additional environment variables for MCP clients
• README.md: replaces references with GROUPS/TOOLS, adds configuration examples and group reference table

How to Configure

# Allow browser automation bundle plus the base tools
GROUPS="browser" 

# Mix multiple bundles with explicit extras
GROUPS="browser,advanced_scraping" TOOLS="extract" 

# Full access still available
PRO_MODE=true 

Everything was tested in both MCP Inspector and Claude Desktop.