fix: preserve Friday equity bars during weekend validation

[stefan-jansen]

Closes #87

Outcome

Equity asset validation now flags only Saturday and Sunday as weekend data. Polars dt.weekday() returns ISO day numbers, so the prior >=5 predicate incorrectly included Friday. The production change is one threshold, >=6.

The public AssetValidator.validate regression exercises valid NYSE/SPY OHLCV rows on each Monday-Friday date and asserts no issues. Saturday/Sunday cases assert the exact weekend issue, preserving weekend detection rather than disabling the check.

Failing base and passing fix

• Affected base/main and immutable v0.2.1: 6888629.
• Regression-only commit: 0cbe5de. Its production src tree is identical to the affected base. With this commit checked out, uv run --no-sync pytest tests/assets/test_validation.py::TestValidateEquity -q -ra exits 1: Friday fails, eight cases pass.
• Fixed head: bf9743e. The same regression command passes all nine cases.
• Exact audit reproduction: datetime(2025, 7, 11, 10), OHLC 100/101/99/100, volume 1000, AssetInfo(symbol="SPY", asset_class=AssetClass.EQUITY, exchange="NYSE"). Before the fix validate returns {'equity_specific': ['Found 1 weekend data points']} instead of {}.
• Verified locally with Polars 1.43.2.

Verification

• Asset, crypto and cross-validation tests with ResourceWarning as an error: 156 passed.
• Repository-wide Ruff, format (336 files), ty and diff checks: passed.
• All 26 applicable PR-head public checks passed, including the full supported-platform test/package matrix, coverage, strict documentation and security. One validated Python 3.15 exception lane is intentionally skipped.
• Full local offline suite: 3,774 passed, 292 deselected, 85.99% coverage. Public coverage lane: 3,774 passed, 86.00% coverage.
• Full local ResourceWarning-as-error lane: 3,774 passed, 292 deselected.
• Actionlint, all-file pre-commit, strict MkDocs, development wheel/sdist builds, twine and isolated artifact installs with dependency/import/CLI/README verification passed.
• Merged main 28677d6 passed all four applicable workflows, with 24 successful checks and two explained skips (PR-only dependency review and the validated Python 3.15 exception). No failed or pending checks remain.

Scope

No calendar API/configuration, provider policy, timezone or holiday architecture changes. Published v0.2.1 and its immutable artifacts are untouched. No new release or documentation deployment is authorized by this repair.

Primary API reference

https://docs.pola.rs/api/python/stable/reference/expressions/api/polars.Expr.dt.weekday.html

AI assistance

AI assisted with reproduction, regression tests and the focused repair. The maintainer owns the executed verification and review.

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