Add app-server marketplace upgrade RPC (#19074)

## Summary
- add a v2 `marketplace/upgrade` app-server RPC that mirrors the
existing configured Git marketplace upgrade path
- expose typed request/response/error payloads and regenerate
JSON/TypeScript schema fixtures
- add app-server integration coverage for all, named, already
up-to-date, and invalid marketplace upgrade requests

## Tests
- `just write-app-server-schema`
- `cargo test -p codex-app-server-protocol`
- `cargo test -p codex-app-server marketplace_upgrade`
- `just fix -p codex-app-server-protocol`
- `just fix -p codex-app-server`
- `just fmt`

codex-rs/app-server-protocol/src/protocol/common.rs

@@ -357,6 +357,10 @@ client_request_definitions! {
         params: v2::MarketplaceRemoveParams,
         response: v2::MarketplaceRemoveResponse,
     },
+    MarketplaceUpgrade => "marketplace/upgrade" {
+        params: v2::MarketplaceUpgradeParams,
+        response: v2::MarketplaceUpgradeResponse,
+    },
     PluginList => "plugin/list" {
         params: v2::PluginListParams,
         response: v2::PluginListResponse,

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

@@ -4104,6 +4104,31 @@ pub struct MarketplaceRemoveResponse {
     pub installed_root: Option<AbsolutePathBuf>,
 }
 
+#[derive(Serialize, Deserialize, Debug, Clone, PartialEq, JsonSchema, TS)]
+#[serde(rename_all = "camelCase")]
+#[ts(export_to = "v2/")]
+pub struct MarketplaceUpgradeParams {
+    #[ts(optional = nullable)]
+    pub marketplace_name: Option<String>,
+}
+
+#[derive(Serialize, Deserialize, Debug, Clone, PartialEq, JsonSchema, TS)]
+#[serde(rename_all = "camelCase")]
+#[ts(export_to = "v2/")]
+pub struct MarketplaceUpgradeResponse {
+    pub selected_marketplaces: Vec<String>,
+    pub upgraded_roots: Vec<AbsolutePathBuf>,
+    pub errors: Vec<MarketplaceUpgradeErrorInfo>,
+}
+
+#[derive(Serialize, Deserialize, Debug, Clone, PartialEq, Eq, JsonSchema, TS)]
+#[serde(rename_all = "camelCase")]
+#[ts(export_to = "v2/")]
+pub struct MarketplaceUpgradeErrorInfo {
+    pub marketplace_name: String,
+    pub message: String,
+}
+
 #[derive(Serialize, Deserialize, Debug, Clone, PartialEq, JsonSchema, TS)]
 #[serde(rename_all = "camelCase")]
 #[ts(export_to = "v2/")]
@@ -9790,6 +9815,36 @@ mod tests {
         );
     }
 
+    #[test]
+    fn marketplace_upgrade_params_serialization_uses_optional_marketplace_name() {
+        assert_eq!(
+            serde_json::to_value(MarketplaceUpgradeParams {
+                marketplace_name: None,
+            })
+            .unwrap(),
+            json!({
+                "marketplaceName": null,
+            }),
+        );
+
+        assert_eq!(
+            serde_json::from_value::<MarketplaceUpgradeParams>(json!({})).unwrap(),
+            MarketplaceUpgradeParams {
+                marketplace_name: None,
+            },
+        );
+
+        assert_eq!(
+            serde_json::to_value(MarketplaceUpgradeParams {
+                marketplace_name: Some("debug".to_string()),
+            })
+            .unwrap(),
+            json!({
+                "marketplaceName": "debug",
+            }),
+        );
+    }
+
     #[test]
     fn plugin_marketplace_entry_serializes_remote_only_path_as_null() {
         assert_eq!(
@@ -10036,6 +10091,37 @@ mod tests {
         );
     }
 
+    #[test]
+    fn marketplace_upgrade_response_serializes_camel_case_fields() {
+        let upgraded_root = if cfg!(windows) {
+            r"C:\marketplaces\debug"
+        } else {
+            "/tmp/marketplaces/debug"
+        };
+        let upgraded_root = AbsolutePathBuf::try_from(PathBuf::from(upgraded_root)).unwrap();
+        let upgraded_root_json = upgraded_root.as_path().display().to_string();
+
+        assert_eq!(
+            serde_json::to_value(MarketplaceUpgradeResponse {
+                selected_marketplaces: vec!["debug".to_string()],
+                upgraded_roots: vec![upgraded_root],
+                errors: vec![MarketplaceUpgradeErrorInfo {
+                    marketplace_name: "broken".to_string(),
+                    message: "failed to clone".to_string(),
+                }],
+            })
+            .unwrap(),
+            json!({
+                "selectedMarketplaces": ["debug"],
+                "upgradedRoots": [upgraded_root_json],
+                "errors": [{
+                    "marketplaceName": "broken",
+                    "message": "failed to clone",
+                }],
+            }),
+        );
+    }
+
     #[test]
     fn codex_error_info_serializes_http_status_code_in_camel_case() {
         let value = CodexErrorInfo::ResponseTooManyFailedAttempts {