Add thread section management APIs (#36380)

## What changed

- Add `threadSection/create`, `threadSection/update`, and `threadSection/delete` app-server methods, with generated protocol schemas and TypeScript bindings.
- Persist custom sections in SQLite with stable UUIDv7 identities, trim and validate display names, and prevent renaming or deleting the built-in pinned section.
- Delete sections transactionally and return their active and archived threads to the unsectioned list.
- Serialize section mutations with section listing so concurrent requests observe ordered updates.

## Testing

- Cover section persistence across restarts, ordered renames, member cleanup on deletion, invalid requests, unsupported stores, and thread-store/state-runtime behavior.

GitOrigin-RevId: dc9a4be283c21dbc93ab1829eafc4825d8df6575

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

@@ -633,9 +633,24 @@ client_request_definitions! {
     },
     ThreadSectionList => "threadSection/list" {
         params: v2::ThreadSectionListParams,
-        serialization: None,
+        serialization: global_shared_read("thread-sections"),
         response: v2::ThreadSectionListResponse,
     },
+    ThreadSectionCreate => "threadSection/create" {
+        params: v2::ThreadSectionCreateParams,
+        serialization: global("thread-sections"),
+        response: v2::ThreadSectionCreateResponse,
+    },
+    ThreadSectionUpdate => "threadSection/update" {
+        params: v2::ThreadSectionUpdateParams,
+        serialization: global("thread-sections"),
+        response: v2::ThreadSectionUpdateResponse,
+    },
+    ThreadSectionDelete => "threadSection/delete" {
+        params: v2::ThreadSectionDeleteParams,
+        serialization: global("thread-sections"),
+        response: v2::ThreadSectionDeleteResponse,
+    },
     #[experimental("thread/search")]
     ThreadSearch => "thread/search" {
         params: v2::ThreadSearchParams,

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

@@ -1139,6 +1139,57 @@ pub struct ThreadSectionListResponse {
     pub next_cursor: Option<String>,
 }
 
+/// Parameters for creating an independently persisted thread section.
+#[derive(Serialize, Deserialize, Debug, Clone, PartialEq, Eq, JsonSchema, TS)]
+#[serde(rename_all = "camelCase")]
+#[ts(export_to = "v2/")]
+pub struct ThreadSectionCreateParams {
+    /// The user-visible name of the section.
+    pub name: String,
+}
+
+/// The independently persisted section created by the server.
+#[derive(Serialize, Deserialize, Debug, Clone, PartialEq, Eq, JsonSchema, TS)]
+#[serde(rename_all = "camelCase")]
+#[ts(export_to = "v2/")]
+pub struct ThreadSectionCreateResponse {
+    pub section: ThreadSection,
+}
+
+/// Parameters for updating an independently persisted thread section.
+#[derive(Serialize, Deserialize, Debug, Clone, PartialEq, Eq, JsonSchema, TS)]
+#[serde(rename_all = "camelCase")]
+#[ts(export_to = "v2/")]
+pub struct ThreadSectionUpdateParams {
+    /// The stable, server-generated identity of the section to update.
+    pub section_id: String,
+    /// The updated user-visible name of the section.
+    pub name: String,
+}
+
+/// The independently persisted section after its name is updated.
+#[derive(Serialize, Deserialize, Debug, Clone, PartialEq, Eq, JsonSchema, TS)]
+#[serde(rename_all = "camelCase")]
+#[ts(export_to = "v2/")]
+pub struct ThreadSectionUpdateResponse {
+    pub section: ThreadSection,
+}
+
+/// Parameters for deleting an independently persisted thread section.
+#[derive(Serialize, Deserialize, Debug, Clone, PartialEq, Eq, JsonSchema, TS)]
+#[serde(rename_all = "camelCase")]
+#[ts(export_to = "v2/")]
+pub struct ThreadSectionDeleteParams {
+    /// The stable, server-generated identity of the section to delete.
+    pub section_id: String,
+}
+
+/// Successful deletion does not return additional section data.
+#[derive(Serialize, Deserialize, Debug, Clone, PartialEq, Eq, JsonSchema, TS)]
+#[serde(rename_all = "camelCase")]
+#[ts(export_to = "v2/")]
+pub struct ThreadSectionDeleteResponse {}
+
 #[derive(Serialize, Deserialize, Debug, Clone, PartialEq, JsonSchema, TS, ExperimentalApi)]
 #[serde(rename_all = "camelCase")]
 #[ts(export_to = "v2/")]