Add .github/copilot-instructions.md for AI agent onboarding

[Copilot]

Adds comprehensive onboarding documentation for AI coding agents working in this Shopify theme repository.

Changes

• Created .github/copilot-instructions.md (410 lines) covering:

  • Project architecture: Vite + Tailwind v4 + Alpine.js + TypeScript + Liquid Ajax Cart v2
  • Repository structure and file purposes
  • Build/dev/deploy workflows and npm scripts
  • Alpine.js auto-registration pattern via import.meta.glob()
  • Path aliases (@/*, ~/* → src/*)
  • Vite plugin stack and custom plugins
  • GitHub Actions workflows (theme-check, deploy-main)

• Documented known issues with workarounds:

  • Missing assets folder warning on first build (expected)
  • 6 moderate npm vulnerabilities in dev dependencies (esbuild, lodash via @shopify/cli-kit)
  • Self-signed SSL certificate workflow for HTTPS dev server
  • Duplicate debounce functions in helpers.js

• Common development patterns:

  • Alpine component/store registration conventions
  • Static asset handling via public/ directory
  • Liquid + Vite integration via auto-generated vite-tag.liquid

Key Technical Details

Shopify theme uses Vite plugin to map source entries to hashed assets:

{% liquid
  render 'vite-tag', entry: 'theme.css'
  render 'vite-tag', entry: 'theme.js'
  render 'vite-tag', entry: '@/js/prodify/index.ts'
%}

Alpine.js modules auto-register via glob imports in src/js/alpine/index.js, enabling drop-in components without manual registration.

MCP configuration (.mcp.json) enables programmatic Shopify dev tools access via @shopify/dev-mcp.

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💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more Copilot coding agent tips in the docs.