Fix: Add missing checkout step to multi-repo-orchestration workflow

[Copilot]

multi-repo-orchestration.yml was failing because actions/setup-python@v5 with cache: 'pip' ran before the repository was checked out, leaving the workspace empty and unable to locate requirements.txt.

Change

Added actions/checkout@v4 between the init echo step and setup-python:

- name: 📥 Checkout Repository
  uses: actions/checkout@v4

- name: 🐍 Setup Python Environment
  uses: actions/setup-python@v5
  with:
    python-version: '3.9'
    cache: 'pip'

This also unblocks .github/scripts/autonomous_git_workflow.py, which was equally unreachable without a prior checkout.

Original prompt

Reference: https://github.com/NguyenCuong1989/Alpha/actions/runs/22710396778/job/65846792256#step:3:1

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