fix: give smoke:web:app its own port; note the App config's era in the table

Copilot review on #1934, both comments actionable:

- smoke:web:app defaulted to 6299 — the same port smoke:web uses — while its
  own comment claimed the port was "distinct … so back-to-back runs can't
  collide". The three web smokes run sequentially in `npm run smoke`, so it
  passed, but a slow teardown, a TIME_WAIT socket, or a parallel run would
  EADDRINUSE it. Moved to 6297 (smoke:web 6299, smoke:web:browser 6298) and
  rewrote the comment to name the actual values rather than assert distinctness.

- The showcase table tells readers to connect with Protocol Era = Modern unless
  noted, and mcp-app-http.json is legacy-only. That was stated in the prose
  below but not in the row, so a reader scanning the table would try Modern
  first. Marked the row.

Verified: smoke:web:app passes standalone on 6297, and the full `npm run smoke`
chain passes with all three web smokes on distinct ports.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XAR2Nr9kXbrywFNUVoTe9F

scripts/smoke-web-app.mjs

@@ -83,8 +83,10 @@ const sandboxProxyPage = join(
 );
 
 const HOST = "127.0.0.1";
-// Distinct from the other web smokes' ports so back-to-back runs can't collide.
-const PORT = process.env.SMOKE_WEB_APP_PORT ?? "6299";
+// Distinct from smoke:web (6299) and smoke:web:browser (6298) so a prior smoke
+// whose port is still bound — slow teardown, TIME_WAIT, or a parallel run —
+// can't EADDRINUSE this one. The three run back-to-back in `npm run smoke`.
+const PORT = process.env.SMOKE_WEB_APP_PORT ?? "6297";
 const TOKEN = "smoke-web-app-token";
 const APP_TOOL = "mcp_app_demo";
 // The URL the test server announces on startup. NOT derived from the config's