Never lose work: atomic saves (temporary file, flush, rename) keeping the replaced version as <file>.bak; autosave of unsaved changes into a recovery folder (every 5 min, preference autosave_minutes, and after commands over 1.5 s; skipped when unchanged; entries locked while their app runs); Recover unsaved design? at launch; doc.recovery_list / doc.recover / doc.recovery_discard; kill-mid-save test

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AS5Tn3xieewUSg3uxrMVdL

crates/engine/src/lib.rs

@@ -10,6 +10,7 @@
 
 pub mod cmd;
 pub mod params;
+pub mod recovery;
 pub mod sample;
 pub mod view;
 
@@ -224,6 +225,10 @@ impl Session {
     pub fn mark_saved(&mut self) {
         self.saved = self.doc.clone();
     }
+    /// The design has changes not in its file (a recovered design).
+    pub fn mark_unsaved(&mut self) {
+        self.saved = Arc::new(Document::new(""));
+    }
 
     pub fn echo(&mut self, s: impl Into<String>) {
         self.log.push(s.into());