Featurizer 0.5.1

Transformer-family label truncation + a cluster of never-executed advanced
aggregator bugs found by stress-testing against three live datasets, plus a
one-hot cardinality guard and CI action bumps.

Added

• High-cardinality one-hot warning. Resolving a role: categorical
  vocabulary (declared list or introspected ENUM) larger than 25 values now
  logs a warning: one-hot encoding emits one sparse 0/1 column per value, which
  is wide and weak. The nudge is to declare a top-N vocabulary: and let the
  long tail fall into the all-zero "other". featurizer stays split-blind (it
  cannot frequency/target-encode — those are fitted, train-only transforms), so
  a warning on the declared/ENUM size is the right lever. Every value is still
  encoded (no silent data loss).

Fixed

• Transformer-family names now survive PostgreSQL's 63-byte identifier cap.
  Every transformer (the base unary path plus the window / rolling / lag / EMA /
  Holt-Winters / diff / cumulative-product / cyclical / binary / population /
  CUSUM / mean-shift families) now routes its output name through
  pg_identifier — a deterministic hash suffix past 63 bytes — and carries a
  full untruncated label. Previously these names were emitted verbatim and
  silently truncated by PostgreSQL at runtime, so a long transformer-wrapped
  name (e.g. ABS(patients.MEAN(visits.ABS(visits.duration_minutes)|interval=P1D))
  at 68 bytes) risked collapsing into an ambiguous column and carried no
  intended name for the manifest. This completes the v0.5.0 manifest-label
  work, which had wired aggregations only; the manifest now maps capped
  transformer columns back to their full names and populates their lineage and
  descriptions. Short names stay byte-identical (the ADR-0007 name-stability
  contract).

• Temporal aggregators are now type-agnostic (date and timestamp columns).
  Stress-testing against three live datasets surfaced dialect bugs that only
  appear when a temporal aggregation runs on a real column: event_rate /
  time_span emitted EXTRACT(EPOCH FROM max - min), invalid on a date
  column (date - date is an integer); the gap_* family / burstiness /
  cross_type_latency differenced raw temporal values, and STDDEV(interval)
  is undefined on timestamp columns. All now extract epoch seconds per side
  and express the result in days (EXTRACT(EPOCH FROM col)/86400.0), which
  is numeric for both types and preserves the original integer-day output on
  date columns. Verified executing on both a date and a timestamp fixture.

• geometric_mean produced invalid SQL — unbalanced parentheses (syntax
  error at else) and base-10 log where the geometric mean needs ln. Now
  case when min(x) > 0 then exp(avg(ln(x))) else null end (NULL on the
  undefined non-positive domain; the ln argument is guarded so the aggregate
  never raises before the outer guard nulls it).

• skewness / kurtosis rewritten as pure-aggregate raw moments. They
  referenced a bare, un-grouped column (invalid in the GROUP BY aggregation
  CTE) and used the ** operator PostgreSQL lacks. Now computed from
  avg(power(x,k)) and var_pop(x) — valid SQL and statistically correct
  (a normal distribution gives kurtosis 3).

Changed

• z_score, min_max_scale, mean_deviation removed from the default
  aggregation set (still registered / requestable). The first two are per-row
  normalizations, not reductions — their SQL references a bare column that is
  invalid inside a GROUP BY aggregate — and are redundant with the
  cross_entity_zscore / cross_entity_percentile transformers.
  mean_deviation nests aggregates (sum(abs(x - avg(x)))), forbidden by
  PostgreSQL; it awaits a SubqueryAggregator rewrite. Removing them keeps a
  wholesale default/wide aggregation sweep valid on real schemas.

• in_array removed from the default transformer set (still registered).
  Its __call__ requires an an_array argument the planner cannot supply, so
  it crashed any wholesale default/wide transform set.