feat: use provider defaults for memory models (#27129)

## Why

Memory startup used hardcoded OpenAI model slugs for extraction and
consolidation. That works for the default OpenAI-compatible path, but
provider-specific backends can require different model identifiers. In
particular, Amazon Bedrock should use its Bedrock model ID for these
background memory requests instead of the OpenAI `gpt-5.4-mini` /
`gpt-5.4` slugs.

## What Changed

- Added provider-owned preferred memory model methods alongside
`approval_review_preferred_model`.
- Updated memory extraction and consolidation to resolve their default
model through the active `ModelProvider`.
- Added Amazon Bedrock overrides so both memory stages use
`openai.gpt-5.4` through Bedrock’s provider-specific model ID.
- Kept explicit `memories.extract_model` and
`memories.consolidation_model` config overrides taking precedence.
- Added startup coverage for default OpenAI and Bedrock memory model
selection.

#closes #26288

codex-rs/memories/write/src/runtime.rs

@@ -13,6 +13,9 @@ use codex_login::AuthManager;
 use codex_login::CodexAuth;
 use codex_login::auth_env_telemetry::collect_auth_env_telemetry;
 use codex_login::default_client::originator;
+use codex_model_provider::ModelProvider;
+use codex_model_provider::SharedModelProvider;
+use codex_model_provider::create_model_provider;
 use codex_otel::SessionTelemetry;
 use codex_otel::TelemetryAuthMode;
 use codex_protocol::SessionId;
@@ -68,6 +71,7 @@ pub(crate) struct MemoryStartupContext {
     thread: Arc<CodexThread>,
     thread_manager: Arc<ThreadManager>,
     auth_manager: Arc<AuthManager>,
+    provider: SharedModelProvider,
     session_telemetry: SessionTelemetry,
 }
 
@@ -79,6 +83,51 @@ impl MemoryStartupContext {
         thread: Arc<CodexThread>,
         config: &Config,
         source: SessionSource,
+    ) -> Self {
+        let provider = create_model_provider(
+            config.model_provider.clone(),
+            Some(Arc::clone(&auth_manager)),
+        );
+        Self::new_with_provider(
+            thread_manager,
+            auth_manager,
+            thread_id,
+            thread,
+            config,
+            source,
+            provider,
+        )
+    }
+
+    #[cfg(test)]
+    pub(crate) fn new_for_testing(
+        thread_manager: Arc<ThreadManager>,
+        auth_manager: Arc<AuthManager>,
+        thread_id: ThreadId,
+        thread: Arc<CodexThread>,
+        config: &Config,
+        source: SessionSource,
+        provider: SharedModelProvider,
+    ) -> Self {
+        Self::new_with_provider(
+            thread_manager,
+            auth_manager,
+            thread_id,
+            thread,
+            config,
+            source,
+            provider,
+        )
+    }
+
+    fn new_with_provider(
+        thread_manager: Arc<ThreadManager>,
+        auth_manager: Arc<AuthManager>,
+        thread_id: ThreadId,
+        thread: Arc<CodexThread>,
+        config: &Config,
+        source: SessionSource,
+        provider: SharedModelProvider,
     ) -> Self {
         let auth = auth_manager.auth_cached();
         let auth = auth.as_ref();
@@ -109,6 +158,7 @@ impl MemoryStartupContext {
             thread,
             thread_manager,
             auth_manager,
+            provider,
             session_telemetry,
         }
     }
@@ -121,6 +171,10 @@ impl MemoryStartupContext {
         self.thread.state_db()
     }
 
+    pub(crate) fn provider(&self) -> &dyn ModelProvider {
+        self.provider.as_ref()
+    }
+
     pub(crate) fn counter(&self, name: &str, inc: i64, tags: &[(&str, &str)]) {
         self.session_telemetry.counter(name, inc, tags);
     }