Add integration tests for running against a real printer

[heikkih]

Summary

• Adds tests/test_integration.py with tests that verify actual API behavior against a real PrusaLink printer
• Registers integration pytest mark and excludes it from default runs via addopts = "-m 'not integration'"
• CI continues to run only unit tests; integration tests never run accidentally
• Adds [project.optional-dependencies] test group for test deps in pyproject.toml

How to run

PRUSALINK_HOST=http://prusa.lan \
PRUSALINK_USERNAME=maker \
PRUSALINK_PASSWORD=secret \
pytest tests/test_integration.py -v -s -m integration

The -m integration flag is required to override the default -m 'not integration' from pyproject.toml.

Why

Mocked unit tests can't reveal what fields the API actually returns. This was highlighted when investigating the job.file.meta structure — we needed a real printer to confirm the actual field names. Integration tests give contributors a reproducible way to verify real behavior before typing it.

Test plan

• Run unit tests without env vars set: pytest tests/ — integration tests should be deselected
• Run integration tests against a real printer with env vars set — all should pass (verified against Core One firmware 6.5.3)

🤖 Generated with Claude Code

[agners]

Btw, maybe we should also start to add our test dependencies to pyproject.toml (as optional dependencies like so):

test = [
  "pytest==9.0.3",
  "pytest-asyncio==1.3.0",
]

[heikkih]

Pushed 1a1e46a addressing the three points:

1. firmware assertion dropped — the get_version() test now only asserts "api" in result, since firmware is missing on MK3.9/6.4.0
2. Docstring updated — added -m integration to the example command so users actually get the tests selected
3. Test extras added — [project.optional-dependencies] test group with pytest, pytest-asyncio, respx

I left requirements-test.txt alone so CI keeps working — the test extras section is purely additive for now. Happy to migrate CI to pip install -e .[test] in a follow-up if you'd like.

Verified locally:

• pytest tests/ — 15 passed, 5 deselected
• pytest tests/test_integration.py -m integration against Core One — 5 passed