Sync dependency sources with setup.py and bootstrap pytest in Copilot sessions

[Copilot]

setup.py dependency updates had drifted from requirements.in, creating inconsistent install surfaces. Copilot sessions also lacked deterministic test bootstrap, so pytest was unavailable unless installed manually.

• Dependency source alignment (requirements.in)

  • Updated package constraints in requirements.in to match setup.py (runtime stack + test tooling), including pinned compatible ranges for requests[security], pandas, dask[dataframe], lxml, pytest, and pytest-cov.
  • Preserves docs/dev entries already managed in requirements.in while removing version drift between install declarations.

• Lockfile refresh (requirements.txt)

  • Recompiled requirements.txt from the updated requirements.in so resolved versions reflect the synchronized constraints.

• Copilot environment bootstrap (.github/workflows/copilot-setup-steps.yml)

  • Added a copilot-setup-steps workflow to preinstall project dependencies in agent sessions:
    • python -m pip install -r requirements.txt
    • python -m pip install -e .
  • Ensures python -m pytest is available in Copilot tasks without ad-hoc dependency installs.

jobs:
  copilot-setup-steps:
    steps:
      - uses: actions/checkout@v5
      - uses: actions/setup-python@v5
        with:
          python-version: "3.12"
      - run: |
          python -m pip install -r requirements.txt
          python -m pip install -e .