[agent-harness] Swap pip → uv in CI workflow

[haasonsaas]

Summary

• Replace python -m pip install --upgrade pip + pip install -e ".[dev]" with astral-sh/[email protected] (pinned by full SHA) followed by uv pip install --system -e ".[dev]".
• No version pin changes, no --user, no pip install -U pip.

Why

Hardens CI against the PyPI partial-read timeouts that took down post-merge evals on main in evalops/maestro-internal#1492. uv resumes partial downloads and retries on connection drops by default, removing a class of transient failures that pip cannot recover from. This workflow has no CLI tool installs, so no uv tool install retry wrapper is needed — that pattern lands when CLI tools show up.

Files changed

• .github/workflows/ci.yml

Test plan

• Confirm all three matrix shards (3.10, 3.11, 3.12) pass Install dependencies.
• Confirm ruff, black, mypy, and pytest steps still resolve binaries from the system env.

🤖 Generated with Claude Code

[cursor]

PR Summary

Low Risk
CI-only change that alters how dependencies are installed; main risk is differences in resolver/install behavior potentially causing CI-only failures.

Overview
Updates the CI workflow to install Python dependencies using uv instead of pip.

Adds an astral-sh/setup-uv step (pinned by SHA) and replaces the previous pip upgrade/install commands with uv pip install --system -e ".[dev]" before running lint/format/typecheck/tests.

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