ci: add GitHub Copilot agent environment setup workflow (#12700)

.github/workflows/copilot-setup-steps.yml

@@ -0,0 +1,78 @@
+name: Copilot Setup Steps
+
+# This workflow defines the setup steps that GitHub Copilot agents will use
+# to prepare the development environment for the oxc project.
+# It preinstalls tools and dependencies needed for Rust and Node.js development.
+
+on:
+  workflow_dispatch:
+  pull_request:
+    types: [opened, synchronize]
+    paths:
+      - .github/workflows/copilot-setup-steps.yml
+  push:
+    branches:
+      - main
+    paths:
+      - .github/workflows/copilot-setup-steps.yml
+
+permissions: {}
+
+jobs:
+  setup:
+    name: Setup Development Environment for Copilot
+    runs-on: ubuntu-latest
+    steps:
+      # Checkout full repo for git history.
+      - uses: actions/checkout@v4
+        with:
+          persist-credentials: false
+
+      - uses: oxc-project/setup-rust@cd82e1efec7fef815e2c23d296756f31c7cdc03d # v1.0.0
+        with:
+          cache-key: copilot
+          save-cache: ${{ github.ref_name == 'main' }}
+          tools: just,watchexec-cli,cargo-insta,typos-cli,cargo-shear,dprint
+
+      - uses: oxc-project/setup-node@f42e3bda950c7454575e78ee4eaac880a077700c # v1.0.0
+
+      - name: Verify installations
+        run: |
+          echo "=== Rust toolchain ==="
+          rustc --version
+          cargo --version
+
+          echo "=== Node.js and pnpm ==="
+          node --version
+          pnpm --version
+
+          echo "=== Command runner ==="
+          just --version
+
+          echo "=== Development tools ==="
+          watchexec --version
+          cargo insta --version
+          typos --version
+          cargo shear --version
+          dprint --version
+
+          echo "=== Project commands ==="
+          just --list
+
+      - name: Setup complete
+        run: |
+          echo "🎉 Development environment setup complete!"
+          echo "The following tools are now available:"
+          echo "  - Rust toolchain (version from rust-toolchain.toml)"
+          echo "  - Node.js and pnpm (versions from .node-version and"
+          echo "    package.json)"
+          echo "  - just command runner"
+          echo "  - Development tools: watchexec, cargo-insta, typos,"
+          echo "    cargo-shear, dprint"
+          echo "  - All Node.js dependencies installed"
+          echo ""
+          echo "You can now use 'just' commands to work with the project:"
+          echo "  - just ready   # Run all checks"
+          echo "  - just fmt     # Format code"
+          echo "  - just test    # Run tests"
+          echo "  - just lint    # Run linting"

AGENTS.md

@@ -68,6 +68,7 @@ just check        # Check code without building
 just test         # Run tests
 just lint         # Run linting
 just doc          # Generate documentation
+just ast          # When directory `crates/oxc_ast` changes
 ```
 
 ### Building and Testing