Render whole-file patches from change metadata

server/src/session/echo.rs

@@ -820,7 +820,7 @@ impl EchoDriver {
                 let id = format!("p-{}", super::random_hex());
                 send(patch_start(
                     id.clone(),
-                    "--- src/example.rs\n+++ src/example.rs\n@@ -1,3 +1,3 @@\n fn answer() -> u8 {\n-    41\n+    42\n }\n"
+                    "--- src/example.rs\n+++ src/example.rs\n@@ -1,3 +1,3 @@\n fn answer() -> u8 {\n-    41\n+    42\n }\n\n--- /dev/null\n+++ notes.md\n+- added bullet\n+added prose\n\n--- old-notes.md\n+++ /dev/null\n-- removed bullet\n-removed prose\n"
                         .to_string(),
                 ));
                 tokio::time::sleep(DELTA_DELAY).await;