Chameleon

Fixed

• The constant-only raw_sql_concat exemption (v4.4.20) worked for TypeScript
  ONLY; Ruby and Python were silently unprotected. _interpolates_only_constants
  extracted the interpolation slot with next(g for g in groups if g is not None),
  but re.findall on the multi-group alternation returns '' (empty string), not
  None, for groups that did not participate -- so it always picked group 1 (the
  TS ${...} slot) and read the Ruby #{...} / Python {...} slot as empty. A
  Rails/Django repositories cohort building safe SQL from a #{TABLE} / {COLUMNS}
  module constant therefore still tripped raw_sql_concat, still lost its canonical
  witness, and (via the paired v4.4.21 change) was emitted witnessless -- the exact
  regression the exemption was written to prevent, in two of the three languages.
  Fixed by testing the slot on truthiness (next((g for g in groups if g), "")),
  which selects the group that actually matched and falls through safely on an
  empty ${}. Found by the step-7 clean-code review.