resolveSearchDefaults no longer accepts a per-call model override and
SearchParams no longer carries limit; neither was reachable from the
tool schema (limit is applied client-side in formatForLLM). Also fold
asPositiveNumber into asPositiveInteger and simplify recency matching.
Run Perplexity search and auth requests through pi's Node runtime instead of
shelling out to Bun. Move development and CI commands to npm, add a Node test
build path, and keep OTP auth fail-fast when Set-Cookie headers are not
available.