Add metrics for extension-rendered skill catalogs (#35597)

## What changed

- Add an optional `ExtensionMetrics` capability to thread, turn-input, and world-state contributors, backed by session telemetry in the host.
- Record skill counts, omissions, and truncated description characters for extension-rendered catalogs, tagged by the catalog surface.
- Preserve host session attribution on extension metrics, including the effective model for each turn, and prevent extension tags from overriding host metadata.
- Avoid duplicate host-catalog samples by recording world-state metrics only when the section is published or changes.

## Testing

- Cover metric values and surface tags, session metadata preservation, turn-level model changes, and host world-state publication behavior.

GitOrigin-RevId: 9059e521943a8f81df25a38b03692eddbc1d990d

codex-rs/ext/extension-api/src/contributors/thread_lifecycle.rs

@@ -1,6 +1,7 @@
 use std::sync::Arc;
 
 use crate::ExtensionData;
+use crate::ExtensionMetrics;
 use codex_mcp::McpResourceClient;
 use codex_protocol::protocol::SessionSource;
 use codex_protocol::protocol::TurnEnvironmentSelection;
@@ -25,6 +26,8 @@ pub struct ThreadStartInput<'a, C> {
     pub environments: &'a [TurnEnvironmentSelection],
     /// MCP resource access supplied by the host for this session.
     pub mcp_resource_client: Option<Arc<McpResourceClient>>,
+    /// Session-attributed metrics supplied by the host.
+    pub extension_metrics: Option<Arc<dyn ExtensionMetrics>>,
     /// Store scoped to the host session runtime.
     pub session_store: &'a ExtensionData,
     /// Store scoped to this thread runtime.

codex-rs/ext/extension-api/src/contributors/world_state.rs

@@ -7,6 +7,7 @@ use codex_protocol::protocol::TurnEnvironmentSelection;
 use serde_json::Value;
 
 use crate::ExtensionData;
+use crate::ExtensionMetrics;
 
 /// Host state available while an extension contributes one sampling step's World State.
 pub struct WorldStateContributionInput<'a> {
@@ -17,6 +18,8 @@ pub struct WorldStateContributionInput<'a> {
     pub ready_selected_capability_roots: &'a [SelectedCapabilityRoot],
     /// Executor-materialized capability files shared by all consumers in this exact step.
     pub executor_capability_discovery: Option<&'a ExecutorCapabilityDiscoverySnapshot>,
+    /// Metrics bound to the effective model for this turn.
+    pub extension_metrics: Option<Arc<dyn ExtensionMetrics>>,
     pub session_store: &'a ExtensionData,
     pub thread_store: &'a ExtensionData,
     pub turn_store: &'a ExtensionData,