Add Instacart marketplace adapter

[ankitranjan7]

Summary

• Add no-key, browser-backed Instacart marketplace adapter commands
• Add stores and categories to discover visible retailers and retailer collection links
• Add storefront, collection, and product to read visible product cards/details
• Add parser tests for retailer, category, product-card, product-detail extraction and typed error behavior

Commands Added

webcmd instacart stores --limit 5
webcmd instacart storefront sprouts --limit 5
webcmd instacart categories sprouts --limit 5
webcmd instacart collection sprouts produce --limit 5
webcmd instacart product 16616932 --retailer sprouts

stores columns: rank, slug, name, delivery, pickup, tags, url.

storefront columns: rank, productId, title, priceText, originalPriceText, discount, size, stock, url.

categories columns: rank, slug, name, url.

collection columns: rank, productId, title, priceText, originalPriceText, discount, size, stock, url.

product columns: productId, title, priceText, originalPriceText, discount, size, stock, retailer, url.

Notes

• Official Instacart Developer Platform endpoints require API-key access, so this PR uses the public marketplace UI and the user's normal CloakBrowser session.
• Store availability, collection order, and product cards depend on the active Instacart location/session.
• Product parsing prefers visible product headings and rejects button-label pollution like Add.
• Collection navigation validates the browser is on the requested collection route before extracting rows, avoiding accidental storefront results after SPA navigation bounces.

Verification

• npm run build-manifest
• npm run test:adapter -- clis/instacart/instacart.test.js
• npm run dev -- instacart stores --limit 3 -f json
• npm run dev -- instacart storefront sprouts --limit 3 -f json
• npm run dev -- instacart categories sprouts --limit 3 -f json
• npm run dev -- instacart collection sprouts produce --limit 3 -f json
• npm run dev -- instacart product 16616932 --retailer sprouts -f json
• npm run dev -- browser work verify instacart/stores --strict-memory
• npm run dev -- browser work verify instacart/storefront --strict-memory
• npm run dev -- browser work verify instacart/categories --strict-memory
• npm run dev -- browser work verify instacart/collection --strict-memory
• npm run dev -- browser work verify instacart/product --strict-memory
• npm run check:silent-column-drop
• npm run check:typed-error-lint
• npm run typecheck
• npm run build