Make turn diff tracking operation backed (#21180)

## Summary
- replace filesystem-based turn diff tracking with an operation-backed
accumulator
- preserve enough verified apply_patch state to render move-overwrite
cases correctly
- keep the turn/diff/updated contract intact while removing remote-only
turn-diff test skips

This takes the assumption that no 3P services rely on the output format
of `apply_patch`

## Why
For the CCA file system isolation push

---------

Co-authored-by: Codex <noreply@openai.com>

codex-rs/apply-patch/src/standalone_executable.rs

@@ -73,7 +73,7 @@ pub fn run_main() -> i32 {
         codex_exec_server::LOCAL_FS.as_ref(),
         /*sandbox*/ None,
     )) {
-        Ok(()) => {
+        Ok(_) => {
             // Flush to ensure output ordering when used in pipelines.
             let _ = stdout.flush();
             0