Add repository-specific Copilot agent instructions

[Copilot]

Changes proposed in this pull request:
This adds a dedicated Copilot instruction file to align cloud-agent behavior with this repository’s workflow and structure, per GitHub Copilot best practices.

• Copilot configuration

  • Added .github/copilot-instructions.md.

• Repository-specific guidance

  • Documented scope expectations for minimal/surgical edits.
  • Documented key paths (containers/, tests/, scripts/init.py, .github/workflows/).
  • Documented standard validation commands and contribution expectations for agent-generated changes.

• Example snippet

## Validation commands
- `python -m pip install -r test-requirements.txt flake8`
- `python -m pytest -q`
- `flake8 .`

Before submitting

• I've read and followed all steps in the Making a pull request
  section of the CONTRIBUTING docs.
• I've updated or added any relevant docstrings following the syntax described in the
  Writing docstrings section of the CONTRIBUTING docs.
• If this PR fixes a bug, I've added a test that will fail without my fix.
• If this PR adds a new feature, I've added tests that sufficiently cover my new functionality.

[espenhgn]

@copilot fix failing checks, update outdated version pins in Dockerfile and build scripts.