fix(app): incremental scrollback search

Search only ran on Enter; typing merely reset the counter to 0/0, so a
visible term showed no matches until the user pressed Enter. run() now takes
an optional query override and onChange fires it on every keystroke for
search-as-you-type, while Enter/Shift+Enter still navigate matches.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

app/src/SearchBar.tsx

@@ -45,16 +45,17 @@ export function SearchBar({
     };
   }, [surfaceId]);
 
-  function run(forward: boolean) {
+  function run(forward: boolean, override?: string) {
     if (!surfaceId) return;
     const addon = getSearch(surfaceId);
-    if (!addon || !term) {
+    const query = override ?? term;
+    if (!addon || !query) {
       addon?.clearDecorations();
       setCount({ index: -1, total: 0 });
       return;
     }
-    if (forward) addon.findNext(term, SEARCH_OPTS);
-    else addon.findPrevious(term, SEARCH_OPTS);
+    if (forward) addon.findNext(query, SEARCH_OPTS);
+    else addon.findPrevious(query, SEARCH_OPTS);
   }
 
   return (
@@ -79,9 +80,14 @@ export function SearchBar({
         ref={inputRef}
         value={term}
         onChange={(e) => {
-          setTerm(e.target.value);
-          setCount({ index: -1, total: 0 });
-          if (surfaceId) getSearch(surfaceId)?.clearDecorations();
+          const value = e.target.value;
+          setTerm(value);
+          if (!value) {
+            setCount({ index: -1, total: 0 });
+            if (surfaceId) getSearch(surfaceId)?.clearDecorations();
+          } else {
+            run(true, value); // search-as-you-type
+          }
         }}
         onKeyDown={(e) => {
           if (e.key === "Enter") {