v0.14.3 — readable dashboard fetch errors

Fixed

• Dashboard fetches surface readable errors instead of raw JSON-parse failures. Any transient non-JSON response (a fleet-proxy hiccup, a restarting member, an HTML error page) hit the 5-second poll as WebKit's SyntaxError: The string did not match the expected pattern. A JSON error body now surfaces its detail/error message, a non-JSON body its HTTP status — and the message self-clears on the next successful poll. The spinup drawer's second bare r.json() reuses the same helper. (#20)