Merge main into fix/1743-render-overwrite-confirm

output_guard joins the split engine lib.rs; the overwrite tests move to tests/render_overwrite.rs
(#2491) and the regression workflow's test filter follows.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01RDvxCS8xcR28VArjzn1x7U

crates/engine/src/render_queue.rs

@@ -110,7 +110,7 @@ pub struct JobShared {
 }
 
 pub(crate) fn lock<T>(m: &Mutex<T>) -> std::sync::MutexGuard<'_, T> {
-    m.lock().unwrap_or_else(|e| e.into_inner())
+    m.lock().unwrap_or_else(std::sync::PoisonError::into_inner)
 }
 
 impl JobShared {