feat: promote 7-day Pro trial in banner, CLI hint, and READMEs

Free-tier launch banner and 'cloakbrowser info' upgrade hint now advertise
the 7-day free Pro trial (Chromium 148) across Python, JS, and .NET; same
CTA added to both READMEs. Also surface binary verification failures verbatim
instead of falling back to a cached build (transient-only fallback).

js/README.md

@@ -252,13 +252,16 @@ free-release model:
 Anti-bot detection updates constantly — an older binary degrades within weeks.
 Pro keeps you on the build that's actively maintained against it.
 
+**New: try the latest Pro binary (Chromium 148) free for 7 days** — see how it
+performs against your targets. Cancel anytime.
+
 Activate with your license key (env var, `licenseKey` option, or `~/.cloakbrowser/license.key`):
 
 ```bash
 export CLOAKBROWSER_LICENSE_KEY=cb_xxxxxxxx
 ```
 
-Pro plans → **[cloakbrowser.dev](https://cloakbrowser.dev)**
+Pro plans & free trial → **[cloakbrowser.dev](https://cloakbrowser.dev)**
 
 ## Requirements