[micro-agent] Swap pip → uv in CI workflow(s)

[haasonsaas]

Summary

• Replace python -m pip install ... setup steps in .github/workflows/ci.yml and .github/workflows/release.yml with uv pip install --system ..., gated on a SHA-pinned astral-sh/setup-uv@08807647e7069bb48b6ef5acd8ec9567f424441b # v8.1.0.
• Drop pip install -U pip warmup. Version pins are unchanged (-e '.[dev]', build).
• python -m build + pypa/gh-action-pypi-publish left untouched in release.yml.

Why

Aligns this repo's CI with the resilience pattern landed in evalops/maestro-internal#1492 (uv resumes partial downloads + retries on connection drops, removing the pip read-timeout flake class).

Scope

• .github/ only. No project-side or Dockerfile changes.
• No CLI-tool installs in either workflow, so the 3-attempt UV_HTTP_TIMEOUT=120 wrapper from #1492 is not used here — kept in reserve if a uv tool install <cli>==<ver> step is added later.

Test plan

• CI workflow green on this PR (test job installs deps via uv pip install --system -e '.[dev]' and runs pytest -q).
• Next tag push exercises the release workflow end-to-end (build via uv pip install --system build → python -m build → publish).

🤖 Generated with Claude Code

[cursor]

PR Summary

Low Risk
Low risk workflow-only change that swaps the installer used in CI/release; main risk is unexpected uv/Python packaging behavior differences causing install or build failures.

Overview
CI and release workflows now use uv for dependency installation. Both .github/workflows/ci.yml and .github/workflows/release.yml add a SHA-pinned astral-sh/setup-uv step and replace pip installs with uv pip install --system (including removal of the pip upgrade warmup).

Release packaging/publishing remains the same aside from installing build via uv before running python -m build.

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