Building on the 4i(d) merge: tag each completion Candidate with a
ModeClass (Both/Advanced/Simple) and, in the hint UI, colour the
continuations by mode ONLY when a candidate list actually mixes modes
(a shared entry word offering both SQL and DSL forms) — Advanced →
theme.mode_advanced, Simple → theme.mode_simple, Both → the token-kind
colour. A single-mode list (the common case, e.g. deep inside a SQL
statement) keeps the token-kind colours, so the tint appears only where
it distinguishes DSL from SQL. With (d)'s Both → Advanced → Simple
block-ordering, each colour reads as one contiguous block.
Candidate gains a `mode` field (typing_surface snapshots regenerated —
uniformly `mode: Both`, no semantic change). Tests: render_candidate_line
mixed-mode colours + the single-mode-keeps-kind-colour rule. Full suite
1913 passing / 0 failing / 1 ignored; clippy clean.
claude@clouddev1
f85261032d