chore(app-server): remove stubbed thread/compact API (#8086)

We want to rely on server-side auto-compaction instead of having the
client trigger context compaction manually. This API was stubbed as a
placeholder and never implemented.

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

@@ -117,10 +117,6 @@ client_request_definitions! {
         params: v2::ThreadListParams,
         response: v2::ThreadListResponse,
     },
-    ThreadCompact => "thread/compact" {
-        params: v2::ThreadCompactParams,
-        response: v2::ThreadCompactResponse,
-    },
     SkillsList => "skills/list" {
         params: v2::SkillsListParams,
         response: v2::SkillsListResponse,