Follow-up to the salvaged #67409 search aliases: with kimi-k3 now in
the curated kimi-coding list (#68108), a Coding Plan key rendered TWO
rows for one model — curated 'kimi-k3' plus live-discovered bare 'k3'
(merge dedup was exact-string). Add model_alias_canonical() derived
from the same alias table and use it as the merge dedup key, so the
curated public slug wins and live-only models still surface.
