fix(stats): add Claude 5 model output pricing

priceForModel() only matched Claude 3/4 prefixes, so claude-*-5 model ids
fell through to null and the Est. saved (USD) line, Pricing for <model>
footer, and (~) parenthetical were silently omitted on Claude 5
sessions. Add the Claude 5 rate card at the top of
MODEL_OUTPUT_PRICE_PER_M (Fable/Mythos 5 $50, Opus 5 $25, Sonnet 5
$10 intro through 2026-08-31 then $15 per shared/provider-catalog,
Haiku 5 $5) and extend the prefix-match regression test, including the
[1m] context variant Claude Code reports.

Signed-off-by: Som Samantray <som.samantray@gmail.com>