add py.type marker and GH actions

[ntner]

Summary

• PEP 561 py.typed marker: The package passes mypy --strict but downstream consumers couldn't benefit from the type annotations without this marker file.
• GitHub Actions CI: Added a unit test + lint workflow on PRs/pushes to master (Python 3.9-3.13 matrix) and a publish-to-PyPI workflow on GitHub release using trusted publishing (OIDC).
• Public stream() method: The README streaming example referenced client._http.stream() (private API). Added client.stream() as a public passthrough and updated the README to use it.

Changes

src/convox/py.typed

• New empty marker file for PEP 561 inline type stub support

src/convox/client.py

• Added ConvoxClient.stream() method that delegates to _http.stream(), with docstring noting the intentional no-raise-on-error behavior for streaming endpoints

README.md

• Updated streaming example from client._http.stream(...) to client.stream(...)
• Updated section description to match

.github/workflows/ci.yml

• Runs on push to master and PRs against master
• Matrix: Python 3.9, 3.10, 3.11, 3.12, 3.13
• Steps: ruff check, ruff format --check, mypy src/, pytest tests/ -v

.github/workflows/publish.yml

• Triggers on GitHub release publish
• Builds with hatch, publishes via pypa/gh-action-pypi-publish using OIDC trusted publishing (no API token secret needed)

Verification

$ pytest tests/ -v          # 172 passed
$ ruff check .              # All checks passed
$ ruff format --check .     # 46 files already formatted
$ mypy src/                 # Success: no issues found in 19 source files

Notes

• The publish workflow uses PyPI trusted publishing (OIDC). You'll need to configure the trusted publisher in PyPI settings for the convox package: set the GitHub repo to convox/convox-python, workflow to publish.yml, and environment to (blank/default).
• No unit test added for client.stream() since it's a one-line passthrough to _http.stream() which is already covered.