fix(telemetry): default telemetry to opt-out with explicit consent UI (#1069)

* fix(telemetry): default telemetry to opt-out with explicit consent UI

* test(webview-ui): add visual snapshot for TelemetryBanner

* fix(webview): guard telemetry queue and fix visual test CI failures

* fix(codecov): cover telemetry guard branch, exempt CT-only fixtures

* fix(telemetry): address parallel-review findings on consent PR

* fix(telemetry): require explicit banner consent