Add an experimental rollout compression endpoint (#46020)

## What changed

Add `rollout/compress` to trigger a best-effort background compression pass for cold local rollouts, even when `features.local_thread_store_compression` is disabled. The method takes no parameters and immediately returns `{}` to acknowledge scheduling, not completion. Existing worker locks, concurrency limits, and cooldowns still apply.

Require the `experimentalApi` capability and reject non-local thread stores. Document the endpoint and the requirement that clients sharing the Codex home support compressed rollout files.

## Testing

Add integration tests for compression with the startup flag disabled, lossless rollout readback, experimental capability enforcement, and rejection of non-local thread stores.

GitOrigin-RevId: be73a3b3f37f3adc54512de8256abf684d5d8112

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

@@ -715,6 +715,13 @@ client_request_definitions! {
         serialization: global("memory"),
         response: v2::MemoryResetResponse,
     },
+    #[experimental("rollout/compress")]
+    /// Start a best-effort background compression pass for cold local rollouts.
+    RolloutCompress => "rollout/compress" {
+        params: #[ts(type = "undefined")] #[serde(skip_serializing_if = "Option::is_none")] Option<()>,
+        serialization: None,
+        response: v2::RolloutCompressResponse,
+    },
     ThreadUnarchive => "thread/unarchive" {
         params: v2::ThreadUnarchiveParams,
         serialization: thread_id(params.thread_id),

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

@@ -30,6 +30,7 @@ mod project;
 mod realtime;
 mod remote_control;
 mod review;
+mod rollout;
 mod thread;
 mod thread_attachment;
 mod thread_data;
@@ -68,6 +69,7 @@ pub use project::*;
 pub use realtime::*;
 pub use remote_control::*;
 pub use review::*;
+pub use rollout::*;
 pub use shared::*;
 pub use thread::*;
 pub use thread_attachment::*;

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

@@ -0,0 +1,13 @@
+//! Fire-and-forget maintenance requests for local rollout storage.
+
+use crate::JsonSchema;
+use crate::TS;
+use serde::Deserialize;
+use serde::Serialize;
+
+/// Acknowledges the compression trigger, not completion. Existing maintenance
+/// locks and cooldowns can cause the background pass to skip without doing work.
+#[derive(Serialize, Deserialize, Debug, Clone, PartialEq, Eq, JsonSchema, TS)]
+#[serde(rename_all = "camelCase")]
+#[ts(export_to = "v2/")]
+pub struct RolloutCompressResponse {}