Fix DiffPanel: preserve base ref on scope switch, fix file scroll target, filter stale refs

- Scope switch (selectGitScope) now preserves diffBaseRef when switching
  to branch scope instead of clearing it via stripDiffSearchParams
- Scroll-to-file useEffect updated to query [data-title] elements (which
  AnnotatableCodeView renders) instead of missing [data-diff-file-path]
- Base ref combobox now filters choices client-side by baseRefQuery text
  so stale/unrelated refs are hidden during refetches

Author: cursoragent

apps/web/src/components/DiffPanel.tsx

@@ -380,7 +380,13 @@ export default function DiffPanel({ mode = "inline", composerDraftTarget }: Diff
   const baseRefItems = [AUTOMATIC_BASE_REF, ...baseRefChoices.map(valueForBaseRefChoice)];
   const filteredBaseRefItems = [
     ...(baseRefQuery.trim().length === 0 ? [AUTOMATIC_BASE_REF] : []),
-    ...baseRefChoices.map(valueForBaseRefChoice),
+    ...baseRefChoices
+      .filter(
+        (choice) =>
+          baseRefQuery.trim().length === 0 ||
+          choice.label.toLowerCase().includes(baseRefQuery.trim().toLowerCase()),
+      )
+      .map(valueForBaseRefChoice),
   ];
   const gitDiff = selectedGitSource?.diff;
 
@@ -436,8 +442,8 @@ export default function DiffPanel({ mode = "inline", composerDraftTarget }: Diff
       return;
     }
     const target = Array.from(
-      patchViewportRef.current.querySelectorAll<HTMLElement>("[data-diff-file-path]"),
-    ).find((element) => element.dataset.diffFilePath === selectedFilePath);
+      patchViewportRef.current.querySelectorAll<HTMLElement>("[data-title]"),
+    ).find((element) => element.textContent?.trim() === selectedFilePath);
     target?.scrollIntoView({ block: "nearest" });
   }, [selectedFilePath, renderableFiles]);
 
@@ -491,8 +497,15 @@ export default function DiffPanel({ mode = "inline", composerDraftTarget }: Diff
       to: "/$environmentId/$threadId",
       params: buildThreadRouteParams(scopeThreadRef(activeThread.environmentId, activeThread.id)),
       search: (previous) => {
+        const prevBaseRef =
+          scope === "branch" ? parseDiffRouteSearch(previous).diffBaseRef : undefined;
         const rest = stripDiffSearchParams(previous);
-        return { ...rest, diff: "1", ...(scope === "unstaged" ? { diffScope: scope } : {}) };
+        return {
+          ...rest,
+          diff: "1",
+          ...(scope === "unstaged" ? { diffScope: scope } : {}),
+          ...(prevBaseRef ? { diffBaseRef: prevBaseRef } : {}),
+        };
       },
     });
   };