Add CI + dev deps; fix test nondeterminism; guard artifact/date-kind drift

[devin-ai-integration]

Summary

Follow-up to the code review of PRs #1–#4. Addresses the gaps that weren't covered there: test reproducibility, missing CI, and unguarded drift risks. No production/UI code changes — only tests, tooling, and CI.

1. Test nondeterminism (from PR #4 review). test_generation.py seeded per-entry RNGs with the built-in hash(title), which is salted per process (PYTHONHASHSEED), so run_tests(seed=42) was not actually reproducible run-to-run (reproduced: 3 runs of the same "seeded" call gave IMG 1828 / 3307 / 9255). Replaced with a stable digest:

def stable_hash(s: str) -> int:
    return int.from_bytes(hashlib.blake2b(s.encode(), digest_size=8).digest(), "big")
# R2/R3 now: random.Random(... stable_hash(e["title"]) ...)

test_common.py verifies it via subprocess under two different PYTHONHASHSEED values → identical output.

2. DATE_KIND_TO_YMD coverage guard (from PR #2 review). Nothing enforced that DATE_KIND_TO_YMD covers every date kind except year; a future kind added to DATE_KIND_LABELS but not DATE_KIND_TO_YMD would make generate_from silently fall through to emitting the raw title. Added test_common.py:

assert set(DATE_KIND_TO_YMD) == set(DATE_KINDS) - {"year"}
assert set(DATE_KINDS) == set(DATE_KIND_LABELS)

3. Artifact-sync guard (from PR #1 review). data.json, data.min.json, and index.html are generated together but committed as static files, so they can silently drift. Added test_artifacts.py:

• data.json == data.min.json
• base64 embedded in index.html decodes back to data.min.json
• regenerating index.html from the committed data.min.json reproduces it byte-for-byte

4. Dev deps + CI (from PR #1 review). pytest/coverage weren't declared anywhere and there was no committed CI workflow, so the tests weren't wired to run automatically. Added requirements-dev.txt and .github/workflows/ci.yml (Python 3.10–3.12) running python3 test_generation.py and pytest.

Verification

• python3 -m pytest -q → 84 passed (77 existing + 7 new).
• python3 test_generation.py → PASS rubric (452 entries, seed=42).
• Reproducibility: same generate_from output under PYTHONHASHSEED=1 and 999.

Link to Devin session: https://app.devin.ai/sessions/c699ea7702c843db9106e378612ebdcb
Requested by: @XVVH

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✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no bugs or issues to report.