v4.6.0

Two schema Stage-2 follow-up items (leased to and delivered by the fleet's
HDB session) plus a round-3 cheap-root cascade:

• PostgreSQL NaN/Infinity/-Infinity NUMERIC support — the three
  special values are now accepted end-to-end (cast, comparison, equality,
  sort, arithmetic, aggregates, predicate pushdown), matching PostgreSQL's
  numeric.c contract: NaN sorts greater than all non-NaN values and
  NaN = NaN is TRUE (deliberately, for btree/GROUP BY/DISTINCT/
  ORDER BY usability, unlike IEEE-754); +Infinity/-Infinity compare and
  propagate through arithmetic as PostgreSQL does (Inf-Inf, Inf/Inf,
  Inf*0 = NaN; finite/Inf = 0; Inf/0 still raises division-by-zero).
• CREATE FUNCTION … RETURNS TABLE(cols) — the composite return form is
  now accepted (previously rejected with "Custom data type not yet
  supported"); the column list is not yet persisted and set-returning
  execution is not yet wired (function calls keep existing scalar behavior).
• Real catalog schema truth (pg_namespace/relnamespace) —
  pg_namespace lists actual registered schemas (no longer hardcoded to
  public); pg_class.relnamespace maps each relation to its real schema's
  oid via a stable, deterministic name→oid map, so the two catalogs join
  consistently. current_schema() is now session-aware; current_schemas(bool)
  added.
• Multi-entry search_path — SET search_path TO a, b now resolves bare
  table references by walking the full ordered list (first match wins),
  replacing the prior first-non-public-entry-only behavior; SHOW search_path
  keeps the established append-public display convention.
• Fix (pre-existing): cross-type foreign keys on the INSERT ... SELECT
  path reported phantom violations (the twin of the direct-INSERT fix in
  4.5.0); now routes through the same type-aware validator, which also fixes
  deferred-FK skip on that path.
• Measured on the PG regression corpus: +14 statements flip to passing across
  both handbacks, 0 regressions.