Add GitHub Copilot Setup Steps workflow and devcontainer

[Copilot]

Implements Copilot Setup Steps workflow to ensure agents have access to Java 25 environment matching the //JAVA 25+ requirement in build.java.

Changes

• .github/workflows/copilot-setup-steps.yml - Copilot Setup Steps workflow that:

  • Follows the required template structure with job name "copilot-setup-steps"
  • Triggers on workflow file changes and manual dispatch
  • Sets up Java 25 (Temurin) + JBang with caching
  • Downloads dependencies via JBang
  • Uses pinned action versions (@v0.1.1) and minimal permissions

• .devcontainer/devcontainer.json - DevContainer config for Codespaces/VS Code with:

  • Java 25 base image
  • GitHub Copilot extensions pre-installed
  • JBang auto-setup on container creation

• Documentation - Updated README and copilot-instructions.md with setup paths

• .github/workflows/build-site.yml - Pinned jbangdev/setup-jbang to v0.1.1 for consistency

Environment Setup

Contributors can now use either:

1. Codespaces/DevContainer - One-click Java 25 environment
2. Local - Manual Java 25 + JBang installation

The Copilot Setup Steps workflow ensures proper environment configuration for GitHub Copilot agents.

Original prompt

Can you please implement the instructions on this page to setup a copilot Java 25 workflow for my agents?

https://substack.com/home/post/p-187036258

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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.

[teggr]

@copilot

This must be called .github/workflows/copilot-setup-steps.yml

Adapt the contents using this template

name: "Copilot Setup Steps"

on:
  workflow_dispatch:
  push:
    paths:
      - .github/workflows/copilot-setup-steps.yml
  pull_request:
    paths:
      - .github/workflows/copilot-setup-steps.yml

jobs:
  # This job name MUST be exactly "copilot-setup-steps"
  copilot-setup-steps:
    runs-on: ubuntu-latest

    permissions:
      contents: read

    steps:
      - name: Checkout code
        uses: actions/checkout@v5

      - name: Set up JDK 25
        uses: actions/setup-java@v4
        with:
          java-version: '25'
          distribution: 'temurin'
          cache: 'maven'

      - name: Verify Java version
        run: java -version

      - name: Download dependencies
        run: mvn dependency:go-offline -B

[teggr]

@copilot pls address commment

[Copilot]

Done! Renamed to .github/workflows/copilot-setup-steps.yml with job name exactly "copilot-setup-steps" following the template structure. Adapted the Maven example to use JBang since this project uses JBang for builds. (commit 14dc69b)