Enable the Bedrock setup wizard by default (#56033)

## What changed

Promote `bedrock_setup_wizard` to stable and enable it by default for eligible onboarding. Users can still disable it with `features.bedrock_setup_wizard = false`.

## Testing

Update onboarding coverage to check the enabled default and explicit opt-out. Remove the explicit opt-in from daemon startup tests so they exercise the default configuration.

GitOrigin-RevId: 5bd911088681a31d34aa444398e6d3f7d1d87955

codex-rs/cli/tests/daemon_startup.rs

@@ -179,7 +179,7 @@ async fn daemon_startup(command: &str) -> Result<()> {
         home.path().join("config.toml"),
         format!(
             "model = \"gpt-5.6-terra\"\n\
-         features.bedrock_setup_wizard = true\ncli_auth_credentials_store = \"file\"\n\
+         cli_auth_credentials_store = \"file\"\n\
          suppress_unstable_features_warning = true\nanalytics.enabled = false\n\
          windows.sandbox = \"unelevated\"\n\
          tui.disable_paste_burst = true\n\

codex-rs/features/src/lib.rs

@@ -2017,8 +2017,8 @@ pub const FEATURES: &[FeatureSpec] = &[
     FeatureSpec {
         id: Feature::BedrockSetupWizard,
         key: "bedrock_setup_wizard",
-        stage: Stage::UnderDevelopment,
-        default_enabled: false,
+        stage: Stage::Stable,
+        default_enabled: true,
     },
     FeatureSpec {
         id: Feature::Personality,

codex-rs/tui/src/lib.rs

@@ -2563,10 +2563,17 @@ requires_openai_auth = {requires_openai_auth}
 
         for (label, config_toml, login_status, target, expected) in [
             (
-                "disabled by default",
+                "enabled by default",
                 "",
                 LoginStatus::NotAuthenticated,
                 AppServerTarget::Embedded,
+                true,
+            ),
+            (
+                "explicitly disabled",
+                "[features]\nbedrock_setup_wizard = false\n",
+                LoginStatus::NotAuthenticated,
+                AppServerTarget::Embedded,
                 false,
             ),
             (