ci: run tests on push and pull request

[dmccoystephenson]

Summary

• Adds .github/workflows/test.yml: compiles graphik.py, runs an import smoke test, and runs the headless pytest suite (SDL_VIDEODRIVER=dummy) on every push to main and every pull request.
• Adds a test optional-dependency group (pytest) to pyproject.toml so CI installs test tooling via pip install -e .[test] instead of a hardcoded pip install pytest line.

Why

The repo has a robust pytest suite (src/test/python/..., 14 tests) and a tag-triggered publish.yml, but no workflow runs on ordinary pushes/PRs — regressions were only caught by manual local validation (py_compile + pytest), which this dev-loop cycle already runs by hand every PR. This gives the same signal automatically and to human reviewers/other contributors.

Scope note

Issue #5 ("Package graphik for proper release & distribution") is intentionally not touched by this PR. Its remaining steps — claiming the graphik name on PyPI (a manual maintainer account action) and migrating downstream consumers (Roam, Apex, Ophidian, Patchwork, Tic-Tak-Toe) off vendored copies (cross-repo follow-ups) — are both outside what this loop can do unilaterally in this repo, per the issue's own latest comment. Left open, no action taken this cycle.

Test plan

• python3 -m py_compile src/main/python/preponderous/graphik/graphik.py
• python3 -c "import preponderous.graphik as g; print(g.__version__)"
• python3 -m pytest -q → 14 passed
• Reviewed test.yml against publish.yml's existing conventions (permissions: contents: read, actions/checkout@v4, actions/setup-python@v5)

[dmccoystephenson]

Self-review rubric:

• Scope: PASS — only .github/workflows/test.yml (new) and a 3-line [project.optional-dependencies] addition to pyproject.toml are touched; both are necessary for the CI workflow, nothing unrelated.
• Tests-new: N/A — this is a CI/build-config change, not a new public method on Graphik; no new test surface is introduced.
• Tests-fix: N/A — not a bug fix, so there is nothing to stash-and-run.
• Sibling structure: PASS — test.yml mirrors publish.yml's existing conventions: header comment explaining purpose, minimal permissions: contents: read, actions/checkout@v4, actions/setup-python@v5.
• Sibling renames: N/A — no identifiers renamed.
• Docs: PASS — grepped README.md/RELEASING.md for CI/workflow mentions; neither claims "no CI exists" or otherwise goes stale from this change, so no doc update needed.
• Issue resolution: N/A — no tracking issue for this gap (found during Phase 1 triage); no Closes #N claimed.
• manual validation: PASS — re-ran on the PR head just now: py_compile succeeds, import smoke test prints 0.2.0, pytest -q → 14 passed.

Repo-specific:

• camelCase: N/A — no new Graphik method added.
• Backward-compat: PASS — no existing public member of Graphik touched.
• Headless: PASS — the new workflow sets SDL_VIDEODRIVER=dummy / SDL_AUDIODRIVER=dummy before running pytest, same as local validation and conftest.py.
• Version sync: N/A — no version string changed.
• No new deps: PASS — pytest is added only under [project.optional-dependencies].test, not dependencies; the runtime dependency set (pygame) and README's "Dependencies" list are unaffected.

Summary: adds the missing push/PR test signal (only a tag-triggered publish workflow existed before); no production code touched, all rubric items pass or are N/A for this change type. Issue #5 (packaging/release) is deliberately not addressed here — its remaining steps are a manual PyPI account action and cross-repo consumer migrations, both outside this PR's scope; noted in the PR body.

[dmccoystephenson]

Independent review pass (inline, via the review skill — no external reviewer available in this dispatch):

Overview: Adds .github/workflows/test.yml (compile + import smoke test + headless pytest on push/PR) and a test optional-dependency group in pyproject.toml. Fills the gap that only a tag-triggered publish.yml existed before.

Findings: No blocking issues.

• Follows publish.yml's existing conventions (minimal permissions: contents: read, actions/checkout@v4, actions/setup-python@v5).
• Headless env vars match conftest.py's pattern.
• Security: read-only token, no secrets referenced, appropriate for pull_request (not pull_request_target).
• Non-blocking polish ideas for a future PR, not required here: a Python version matrix to actually exercise the declared requires-python = ">=3.8" range (currently only latest 3.x runs), cache: pip on setup-python for speed, and a concurrency group to cancel superseded runs.

No changes requested. Manual validation remains green (py_compile, import smoke test, pytest 14/14).

[dmccoystephenson]

Self-review: fixed CI failure by pinning python-version to 3.13 (pygame has no cp314 wheel yet). Verified locally with pytest -q (14 passed); Compile and test check on this PR is now green. Filed #15 for the same latent issue in publish.yml (out of scope here).