Root package.json declared no main or exports, so OpenCode npm plugin
resolution (import.meta.resolve) failed and the plugin was silently
skipped (#3127). The .opencode TypeScript sources imported siblings
with .js specifiers that only exist after compilation, so the home
install, which loads the .ts files in place, crashed the tool registry
with ERR_MODULE_NOT_FOUND (#3112).
Declare main/types/exports on the root package pointing at the
compiled plugin entry, switch the sources to .ts specifiers, and
enable allowImportingTsExtensions with rewriteRelativeImportExtensions
so the emitted dist keeps working .js specifiers. Add smoke tests that
build the package, resolve and import the entry by name from a temp
install, and verify every in-place relative import resolves.
Fixes#3127Fixes#3112
Affaan Mustafa