[codex] show external import result counts (#29567)

## What changed

- Show per-type import counts in the `/import` review UI and started
message.
- Render completion results as a multi-line summary with total
imported/failed counts and one row per import type.
- Add snapshot coverage for the updated review and completion output.

<img width="537" height="322" alt="Screenshot 2026-06-23 at 9 41 20 PM"
src="https://github.com/user-attachments/assets/166542eb-2097-4b2b-8130-8f6fd8c680ce"
/>


## Why

The TUI previously only reported that Claude Code import started or
finished. Users could not see how many items of each type were selected
or how many actually imported versus failed.

codex-rs/app-server-protocol/src/protocol/v2/config.rs

@@ -574,6 +574,13 @@ pub struct PluginsMigration {
     pub plugin_names: Vec<String>,
 }
 
+#[derive(Serialize, Deserialize, Debug, Clone, PartialEq, Eq, JsonSchema, TS)]
+#[serde(rename_all = "camelCase")]
+#[ts(export_to = "v2/")]
+pub struct SkillMigration {
+    pub name: String,
+}
+
 #[derive(Serialize, Deserialize, Debug, Clone, PartialEq, Eq, JsonSchema, TS)]
 #[serde(rename_all = "camelCase")]
 #[ts(export_to = "v2/")]
@@ -618,6 +625,8 @@ pub struct MigrationDetails {
     #[serde(default)]
     pub plugins: Vec<PluginsMigration>,
     #[serde(default)]
+    pub skills: Vec<SkillMigration>,
+    #[serde(default)]
     pub sessions: Vec<SessionMigration>,
     #[serde(default)]
     pub mcp_servers: Vec<McpServerMigration>,