chore(features) Personality => Stable (#10310)

## Summary
Bump `/personality` to stable

## Testing
 - [x] unit tests pass

codex-rs/core/src/config/mod.rs

@@ -3811,7 +3811,7 @@ model_verbosity = "high"
                 model_reasoning_summary: ReasoningSummary::Detailed,
                 model_supports_reasoning_summaries: None,
                 model_verbosity: None,
-                personality: None,
+                personality: Some(Personality::Friendly),
                 chatgpt_base_url: "https://chatgpt.com/backend-api/".to_string(),
                 base_instructions: None,
                 developer_instructions: None,
@@ -3896,7 +3896,7 @@ model_verbosity = "high"
             model_reasoning_summary: ReasoningSummary::default(),
             model_supports_reasoning_summaries: None,
             model_verbosity: None,
-            personality: None,
+            personality: Some(Personality::Friendly),
             chatgpt_base_url: "https://chatgpt.com/backend-api/".to_string(),
             base_instructions: None,
             developer_instructions: None,
@@ -3996,7 +3996,7 @@ model_verbosity = "high"
             model_reasoning_summary: ReasoningSummary::default(),
             model_supports_reasoning_summaries: None,
             model_verbosity: None,
-            personality: None,
+            personality: Some(Personality::Friendly),
             chatgpt_base_url: "https://chatgpt.com/backend-api/".to_string(),
             base_instructions: None,
             developer_instructions: None,
@@ -4082,7 +4082,7 @@ model_verbosity = "high"
             model_reasoning_summary: ReasoningSummary::Detailed,
             model_supports_reasoning_summaries: None,
             model_verbosity: Some(Verbosity::High),
-            personality: None,
+            personality: Some(Personality::Friendly),
             chatgpt_base_url: "https://chatgpt.com/backend-api/".to_string(),
             base_instructions: None,
             developer_instructions: None,

codex-rs/core/src/features.rs

@@ -564,12 +564,8 @@ pub const FEATURES: &[FeatureSpec] = &[
     FeatureSpec {
         id: Feature::Personality,
         key: "personality",
-        stage: Stage::Experimental {
-            name: "Personality",
-            menu_description: "Choose a communication style for Codex.",
-            announcement: "NEW: Pick a personality for Codex. Enable in /experimental!",
-        },
-        default_enabled: false,
+        stage: Stage::Stable,
+        default_enabled: true,
     },
     FeatureSpec {
         id: Feature::ResponsesWebsockets,