build(test-multiprocessing): Migrate to uv and pyproject.toml

[ericapisani]

Summary

• Replace pip/requirements.txt with uv/pyproject.toml for dependency management
• Update run.sh to use uv run instead of manual venv creation and pip install
• Remove legacy requirements.txt

Refs PY-2465

Test plan

• Verify pyproject.toml includes all dependencies from the original requirements.txt
• Verify run.sh uses uv run
• Verify requirements.txt is removed

🤖 Generated with Claude Code

[linear-code]

PY-2465

[sentry]

Bug: The pyproject.toml requires Python >=3.12, but the .python-version file is pinned to 3.9, causing uv run to fail.
_{Severity: HIGH}

Suggested Fix

Align the Python versions. Either update the .python-version file to a version that satisfies >=3.12 (e.g., 3.12), or adjust the requires-python constraint in pyproject.toml to be compatible with 3.9 (e.g., >=3.9).

Prompt for AI Agent

Review the code at the location below. A potential bug has been identified by an AI
agent. Verify if this is a real issue. If it is, propose a fix; if not, explain why it's
not valid.

Location: test-multiprocessing/pyproject.toml#L4

Potential issue: The `pyproject.toml` file specifies a `requires-python` constraint of
`>=3.12`. However, the `.python-version` file in the same directory pins the Python
version to `3.9`. When `uv run python main.py` is executed, `uv` detects this version
incompatibility between the project's requirement and the specified local version,
leading to an error and failure of the command.

_{Did we get this right? 👍 / 👎 to inform future reviews.}

[sentry]

Bug: The run.sh script installs uv but fails to use it immediately after, as the PATH is not updated in the current shell session.
_{Severity: HIGH}

Suggested Fix

After installing uv, update the PATH in the current shell session before calling uv run. For example, add export PATH="$HOME/.cargo/bin:$PATH" or a similar command appropriate for the uv installation path.

Prompt for AI Agent

Review the code at the location below. A potential bug has been identified by an AI
agent. Verify if this is a real issue. If it is, propose a fix; if not, explain why it's
not valid.

Location: test-multiprocessing/run.sh#L5-L9

Potential issue: In an environment where `uv` is not pre-installed, the `run.sh` script
attempts to install it. However, the installation script only modifies shell profile
files (e.g., `.bashrc`) and does not update the `PATH` for the current, non-interactive
shell session. Because the script immediately calls `uv run` and uses `set -e`, the
execution halts with a "command not found" error, preventing the script from completing.

_{Did we get this right? 👍 / 👎 to inform future reviews.}