[proto] Swap pip → uv in CI workflow

[haasonsaas]

Summary

• Replace pip with uv in the python-package job of .github/workflows/ci.yml.
• build is now installed via astral-sh/setup-uv@08807647e7069bb48b6ef5acd8ec9567f424441b # v8.1.0 + uv tool install build, wrapped in a 3-attempt retry with UV_HTTP_TIMEOUT=120. Invoke it as pyproject-build (the CLI shim build exposes).
• Smoke-install of the generated wheel now uses uv pip install dist/*.whl inside the existing .venv-smoke venv.
• Dropped both python -m pip install --upgrade pip self-upgrades; no --user was in use.

Why

Mirrors the pattern from evalops/maestro-internal#1492, where pip stalled on a partial-read timeout and uv (with its resume + retry semantics, plus an explicit 3-attempt wrapper) eliminated the flake. Same shape applied here so proto CI doesn't trip on the same class of PyPI hiccup.

Files changed

• .github/workflows/ci.yml — only file in .github/ with pip install / python -m pip hits.

Test plan

• python-package job passes on this PR (build wheel + smoke install + import-all check).
• No version drift in installed build (uv resolves latest, matching prior behavior — no version was previously pinned).
• Other jobs (lint, breaking, generate, go-test, ts-package) unaffected.

🤖 Generated with Claude Code

[cursor]

PR Summary

Low Risk
Low risk: only updates CI tooling for Python wheel build and smoke install, with a small chance of CI behavior differences due to uv/pyproject-build resolution changes and the new retry logic.

Overview
Updates the python-package CI job to use uv instead of pip for building and smoke-installing the generated Python wheel.

Adds astral-sh/setup-uv, installs build via uv tool install build with a 3-attempt retry + increased UV_HTTP_TIMEOUT, runs pyproject-build, and switches the smoke install to uv pip install (dropping the prior pip self-upgrade steps).

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