fix: two manifest validation gaps (single-list NaN handling, RowFilter operator)

[propcgamer20-png]

#547 - disadvantaged_mask treats NaN as "known" in the single-list branches

ProtectedAttribute.disadvantaged_mask's branches for "only disadvantaged_values" or "only advantaged_values" given hardcoded known = pd.Series(True, index=df.index). A NaN in the column matches neither isin() nor its complement, so it was silently classified to one side instead of excluded - contradicting the module's own docstring and inconsistent with the both-lists branch, numeric_threshold, and age_interval_threshold, which all exclude unclassifiable rows via known_mask.

pa = ProtectedAttribute(name="race", type="categorical", column="race",
                        advantaged_values=["White", "Asian-Pac-Islander"])
mask, known = pa.disadvantaged_mask(pd.DataFrame({"race": ["White", "Black", None]}))
# before: disadv [F, T, T]   known [T, T, T]   <- NaN counted as disadvantaged
# after:  disadv [F, T, F]   known [T, T, F]   <- NaN excluded

Benefits Denial/audit.yaml uses the single-list pattern for race and national_origin, so a real missing value there would corrupt the fairness gap. Fix: known = col.notna() in both single-list branches.

#549 - RowFilter has no validation that an operator is set

Unlike TargetSpec and ProtectedAttribute (which validate required companion fields in __post_init__), RowFilter had none. A block with column set but no operator silently kept every row:

RowFilter(column="race").apply(df)   # returned df unchanged, no error

MANIFEST_SPEC.md documents "exactly one of the operators below" as required. Added __post_init__ raising ValueError when none of isin / not_isin / equals / not_equals / notna is set.

Tests

• test_categorical_single_list_excludes_nan_via_known_mask (parametrized over both single-list branches)
• test_row_filter_needs_at_least_one_operator

pytest tests/test_manifest.py -> all pass (33 -> 36), including test_every_shipped_manifest_loads_without_error (no shipped audit.yaml has an operator-less filter). ruff clean. The 3 tests/test_benchmark.py failures are pre-existing on main on this platform (manifest-error-wrapping path checks) and unrelated.

Closes #547
Closes #549

[vercel]

@propcgamer20-png is attempting to deploy a commit to the yashkewlani2020-gmailcom's projects Team on Vercel.

A member of the Team first needs to authorize it.

[github-actions]

@yakew7 @ahmdkaml - new PR touching a path you own, please review.