chore: stop consuming legacy config profiles (#24076)

## Why

The old config-profile mechanism should no longer influence runtime
behavior now that profile selection has moved to file-based `--profile`
config files. Core already rejects a selected legacy `profile = "..."`
with a migration error in
[`core/src/config/mod.rs`](https://github.com/openai/codex/blob/d6451fcb79edc4a71bc9e811bcda06fd3c36562e/codex-rs/core/src/config/mod.rs#L2521-L2529),
but a few residual consumers still read legacy `[profiles.*]` data while
performing managed-feature checks and personality migration.

That kept dead legacy profile state relevant after selection had been
removed, and could make personality migration depend on a stale or
missing old profile.

## What changed

- Stop scanning legacy `[profiles.*]` feature settings when validating
managed feature requirements.
- Make personality migration consider only top-level `personality` and
`model_provider` settings.
- Remove the now-unused `ConfigToml::get_config_profile` helper.
- Update personality migration coverage to verify that legacy profile
personality fields and missing legacy profile names no longer affect
that migration path.

This keeps the legacy `profile` / `profiles` config shape available for
the remaining compatibility and migration diagnostics; it only removes
these behavior consumers.

## Verification

- Updated `core/tests/suite/personality_migration.rs` for the new
legacy-profile behavior.
- Focused test command: `cargo test -p codex-core
personality_migration`.

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

@@ -9,7 +9,6 @@ use codex_config::RequirementSource;
 use codex_config::Sourced;
 
 use codex_config::config_toml::ConfigToml;
-use codex_config::profile_toml::ConfigProfile;
 use codex_features::Feature;
 use codex_features::FeatureConfigSource;
 use codex_features::FeatureOverrides;
@@ -269,27 +268,6 @@ fn explicit_feature_settings_in_config(cfg: &ConfigToml) -> Vec<(String, Feature
             enabled,
         ));
     }
-    for (profile_name, profile) in &cfg.profiles {
-        if let Some(features) = profile.features.as_ref() {
-            for (key, enabled) in features.entries() {
-                if let Some(feature) = feature_for_key(&key) {
-                    explicit_settings.push((
-                        format!("profiles.{profile_name}.features.{key}"),
-                        feature,
-                        enabled,
-                    ));
-                }
-            }
-        }
-        if let Some(enabled) = profile.experimental_use_unified_exec_tool {
-            explicit_settings.push((
-                format!("profiles.{profile_name}.experimental_use_unified_exec_tool"),
-                Feature::UnifiedExec,
-                enabled,
-            ));
-        }
-    }
-
     explicit_settings
 }
 
@@ -339,47 +317,13 @@ pub(crate) fn validate_feature_requirements_in_config_toml(
     cfg: &ConfigToml,
     feature_requirements: Option<&Sourced<FeatureRequirementsToml>>,
 ) -> std::io::Result<()> {
-    fn validate_profile(
-        cfg: &ConfigToml,
-        profile_name: Option<&str>,
-        profile: &ConfigProfile,
-        feature_requirements: Option<&Sourced<FeatureRequirementsToml>>,
-    ) -> std::io::Result<()> {
-        let configured_features = Features::from_sources(
-            FeatureConfigSource {
-                features: cfg.features.as_ref(),
-                experimental_use_unified_exec_tool: cfg.experimental_use_unified_exec_tool,
-            },
-            FeatureConfigSource {
-                features: profile.features.as_ref(),
-                experimental_use_unified_exec_tool: profile.experimental_use_unified_exec_tool,
-            },
-            FeatureOverrides::default(),
-        );
-        ManagedFeatures::from_configured(configured_features, feature_requirements.cloned())
-            .map(|_| ())
-            .map_err(|err| {
-                if let Some(profile_name) = profile_name {
-                    std::io::Error::new(
-                        err.kind(),
-                        format!(
-                            "invalid feature configuration for profile `{profile_name}`: {err}"
-                        ),
-                    )
-                } else {
-                    err
-                }
-            })
-    }
-
-    validate_profile(
-        cfg,
-        /*profile_name*/ None,
-        &ConfigProfile::default(),
-        feature_requirements,
-    )?;
-    for (profile_name, profile) in &cfg.profiles {
-        validate_profile(cfg, Some(profile_name), profile, feature_requirements)?;
-    }
-    Ok(())
+    let configured_features = Features::from_sources(
+        FeatureConfigSource {
+            features: cfg.features.as_ref(),
+            experimental_use_unified_exec_tool: cfg.experimental_use_unified_exec_tool,
+        },
+        FeatureConfigSource::default(),
+        FeatureOverrides::default(),
+    );
+    ManagedFeatures::from_configured(configured_features, feature_requirements.cloned()).map(|_| ())
 }

codex-rs/core/src/personality_migration.rs

@@ -32,17 +32,14 @@ pub async fn maybe_migrate_personality(
         return Ok(PersonalityMigrationStatus::SkippedMarker);
     }
 
-    let config_profile = config_toml
-        .get_config_profile(/*override_profile*/ None)
-        .map_err(|err| io::Error::new(io::ErrorKind::InvalidData, err))?;
-    if config_toml.personality.is_some() || config_profile.personality.is_some() {
+    if config_toml.personality.is_some() {
         create_marker(&marker_path).await?;
         return Ok(PersonalityMigrationStatus::SkippedExplicitPersonality);
     }
 
-    let model_provider_id = config_profile
+    let model_provider_id = config_toml
         .model_provider
-        .or_else(|| config_toml.model_provider.clone())
+        .clone()
         .unwrap_or_else(|| "openai".to_string());
 
     if !has_recorded_sessions(codex_home, model_provider_id.as_str(), state_db).await? {