feat(safeway): add read-only MCP server

[walkerhughes]

Summary

• add a Safeway plugin compatible with Claude Code and Codex
• expose read-only store lookup, store-scoped product search, product refresh, and shopping-list pricing tools
• add a shopping and menu-planning skill with explicit price, promotion, and inventory boundaries
• cover the browser-facing contracts and task-shaped tools with unit tests

Verification

• make check
• make coverage (89%)
• official Codex plugin validator
• official skill validator

Safety

This integration uses undocumented public browser-facing Safeway contracts. It does not access accounts, coupons, carts, ordering, or checkout. Prices and inventory are returned with store and fulfillment context and are not guarantees.