Both Node::Ident and Word carried a highlight_override field, and
both were dead — the walker driver discarded the Ident's and
walk_word hardcoded Keyword. So column types (int, serial, …)
rendered identically to table/column names.
Wire both overrides through, and add a dedicated HighlightClass::Type
with its own theme colour (tok_type), distinct from keyword-purple
and identifier-teal. The three type Ident slots opt in, so canonical
types and the advanced-mode single-word SQL aliases (float, varchar,
…) render as types; the two-word `double precision` alias opts in via
a new Word::type_keyword constructor. ADR-0022 Amendment 4.
claude@clouddev1
d20f765325