cost-estimate.js carries its own copy of the stale Opus/Haiku/Sonnet rate
table already reported in #2574, but grepping every .js/.json/.md file
outside node_modules turns up zero callers besides its own test. It was
added in 940135e alongside the statusline observability hooks and never
wired into any of them.
The maintainer's comment on #2656 named two acceptable outcomes: remove
the unused duplicate, or share one rate source with the live tracker.
cost-tracker.js's own fix (#2574) has not landed yet, so sharing its
table now would import numbers that are still wrong. Removing the dead
file is the smaller, immediately-correct step.
Fixes#2656
