The studio sees a preview the instant it serves: listen for `app.serving` #89

Pushed.

The live client's KINDS now includes app.serving, and onEvent refreshes the app fragment (refreshApp) on it the same way it does for a deploy run event — matched on the event's own kind plus payload.app/payload.env (never on payload.kind === 'deploy', which app.serving doesn't carry), reusing the existing single-flight/queued-refresh guard so a burst of run.started, app.serving, run.finished still collapses to one fetch in flight and one queued. On non-app pages app.serving falls through to the same generic pill-only handling every other unmatched event kind already gets.

Added:

• test/live-pages.test.ts: the studio app page's served script now contains app.serving (fails on the old code).
• test/studio.test.ts: publishes an app.serving event with the real payload shape (app, env, commitOid, servingAt, testsRunning) and asserts it reaches the repo's SSE stream while the deploy run is still running — the exact gap the issue names.

bun x tsc --noEmit and the forge's check test list both pass; the 6 pre-existing failures in apps.test.ts/pulls.test.ts/web.test.ts/cross-repo-pull.test.ts are git-push-auth environment issues, reproduced identically with my changes stashed out, so they're unrelated to this change.

Closes #81