chore: split memories part 1 (#19818)

Extract memories into 2 different crates

codex-rs/core/src/session/mod.rs

@@ -3323,7 +3323,7 @@ fn errors_to_info(errors: &[SkillError]) -> Vec<SkillErrorInfo> {
         .collect()
 }
 
-use crate::memories::prompts::build_memory_tool_developer_instructions;
+use codex_memories_read::build_memory_tool_developer_instructions;
 
 #[cfg(test)]
 pub(crate) mod tests;