The example plugin is a Yaegi entrypoint evaluated at runtime through its
exported factory functions, so it has no func main. As a regular package main
it broke `go build ./...` with "function main is undeclared in the main
package".
Add //go:build ignore so the go tool skips it. Yaegi is unaffected: the loader
reads the file and calls interp.Eval on its source, which does not evaluate
build constraints.
Fixes#3478
Demonstrates all plugin capabilities: authenticated and unauthenticated
routes, event listeners, and lifecycle hooks. Uses a shared singleton
for factory functions so Init() state is available to route handlers.
kolaente
