[codex] reduce module visibility (#16978)

## Summary
- reduce public module visibility across Rust crates, preferring private
or crate-private modules with explicit crate-root public exports
- update external call sites and tests to use the intended public crate
APIs instead of reaching through module trees
- add the module visibility guideline to AGENTS.md

## Validation
- `cargo check --workspace --all-targets --message-format=short` passed
before the final fix/format pass
- `just fix` completed successfully
- `just fmt` completed successfully
- `git diff --check` passed

codex-rs/core/src/rollout.rs

@@ -1,17 +1,26 @@
 use crate::config::Config;
 pub use codex_rollout::ARCHIVED_SESSIONS_SUBDIR;
+pub use codex_rollout::Cursor;
+pub use codex_rollout::EventPersistenceMode;
 pub use codex_rollout::INTERACTIVE_SESSION_SOURCES;
 pub use codex_rollout::RolloutRecorder;
 pub use codex_rollout::RolloutRecorderParams;
 pub use codex_rollout::SESSIONS_SUBDIR;
 pub use codex_rollout::SessionMeta;
+pub use codex_rollout::ThreadItem;
+pub use codex_rollout::ThreadSortKey;
+pub use codex_rollout::ThreadsPage;
 pub use codex_rollout::append_thread_name;
 pub use codex_rollout::find_archived_thread_path_by_id_str;
 #[deprecated(note = "use find_thread_path_by_id_str")]
 pub use codex_rollout::find_conversation_path_by_id_str;
 pub use codex_rollout::find_thread_name_by_id;
+pub use codex_rollout::find_thread_names_by_ids;
 pub use codex_rollout::find_thread_path_by_id_str;
 pub use codex_rollout::find_thread_path_by_name_str;
+pub use codex_rollout::parse_cursor;
+pub use codex_rollout::read_head_for_summary;
+pub use codex_rollout::read_session_meta_line;
 pub use codex_rollout::rollout_date_parts;
 
 impl codex_rollout::RolloutConfigView for Config {
@@ -36,24 +45,30 @@ impl codex_rollout::RolloutConfigView for Config {
     }
 }
 
-pub mod list {
-    pub use codex_rollout::list::*;
+pub(crate) mod list {
+    pub use codex_rollout::ThreadListConfig;
+    pub use codex_rollout::ThreadListLayout;
+    pub use codex_rollout::ThreadSortKey;
+    pub use codex_rollout::find_thread_path_by_id_str;
+    pub use codex_rollout::get_threads_in_root;
 }
 
 pub(crate) mod metadata {
-    pub(crate) use codex_rollout::metadata::builder_from_items;
+    pub(crate) use codex_rollout::builder_from_items;
 }
 
-pub mod policy {
-    pub use codex_rollout::policy::*;
+pub(crate) mod policy {
+    pub use codex_rollout::EventPersistenceMode;
+    pub use codex_rollout::should_persist_response_item_for_memories;
 }
 
-pub mod recorder {
-    pub use codex_rollout::recorder::*;
+pub(crate) mod recorder {
+    pub use codex_rollout::RolloutRecorder;
 }
 
-pub mod session_index {
-    pub use codex_rollout::session_index::*;
+pub(crate) mod session_index {
+    pub use codex_rollout::append_thread_name;
+    pub use codex_rollout::find_thread_name_by_id;
 }
 
 pub(crate) use crate::session_rollout_init_error::map_session_init_error;