Framework integration

WRNexusJS 0.4 discovers components and browser runtimes from installed package plugins.

@wrnexus/captcha is a complete example:

packages/captcha/package.json declares wrnexus.plugin.
captchaPlugin() contributes its component directory, client runtime, Tailwind source, and DevToolbar audit panel.
Captcha.wrn renders data-wrnexus-runtime="captcha".
SSR injects the runtime only when the component appears.
CSR navigation mounts and unmounts the runtime.
Development serves the package source; production emits a hashed chunk.

There is intentionally no packages/ui/components/Captcha.wrn, no showcase-local copy, and no public captcha.js file.

integration/platform-upgrade.test.ts exercises the 0.4 cross-package foundation.