feat: cache and revalidate the discovered catalog

Serve the last discovered catalog from plugin storage at startup
(stale-while-revalidate) so the model picker is populated without waiting
on the network, then refresh in the background and replay the transform
only when the catalog changed. Revalidate on an interval too, default
every five minutes, configurable via refreshMs (0 disables polling);
concurrent polls are coalesced.

A revalidation can no longer strip reasoning variants: a failed or
incomplete reasoning-level read now carries the previous catalog's
variants forward instead of caching the loss. A missing Codex client
catalog (404) is an empty answer rather than a failure. The cache never
stores the API key.

Also ship the root index.js wrapper in the npm package (required by
OpenCode 2's plugin directory scan) and release as 0.2.0.

Merge pull request yourcasualdev#3 from yourcasualdev/release/npm-tru…

…sted-publishing

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Release v0.1.1

Release v0.1.0