fix(editor): default the plan diff view to Classic

AGENTS.md

@@ -830,8 +830,9 @@ When a user denies a plan and Claude resubmits, the UI shows what changed betwee
 
 **Diff engine** (`packages/ui/utils/planDiffEngine.ts`): Uses the `diff` npm package (`diffLines()`) to compute line-level diffs. Groups consecutive remove+add into "modified" blocks. Returns `PlanDiffBlock[]` and `PlanDiffStats`.
 
-**Two view modes** (toggle via `PlanDiffModeSwitcher`):
-- **Rendered** (`PlanCleanDiffView`): Color-coded left borders — green (added), red (removed/strikethrough), yellow (modified)
+**Three view modes** (toggle via `PlanDiffModeSwitcher`; `planDiffMode` in `packages/editor/App.tsx` defaults to `classic`):
+- **Classic** (`PlanCleanDiffView`, block-level, old above new): Color-coded left borders — green (added), red (removed/strikethrough), yellow (modified). The default.
+- **Rendered** (`PlanCleanDiffView` with `wordLevel`, experimental): the same view with word-level inline highlighting.
 - **Raw** (`PlanRawDiffView`): Monospace `+/-` lines, git-style
 
 **State** (`packages/ui/hooks/usePlanDiff.ts`): Manages base version selection, diff computation, and version fetching. The server sends `previousPlan` with the initial `/api/plan` response; the hook auto-diffs against it. Users can select any prior version from the sidebar Version Browser.

packages/editor/App.tsx

@@ -670,7 +670,7 @@ const App: React.FC = () => {
 
   const [initialExportTab, setInitialExportTab] = useState<'share' | 'annotations' | 'notes'>();
   const [isPlanDiffActive, setIsPlanDiffActive] = useState(false);
-  const [planDiffMode, setPlanDiffMode] = useState<PlanDiffMode>('clean');
+  const [planDiffMode, setPlanDiffMode] = useState<PlanDiffMode>('classic');
   const [previousPlan, setPreviousPlan] = useState<string | null>(null);
   const [versionInfo, setVersionInfo] = useState<VersionInfo | null>(null);
   const [aiSessionEnabled, setAISessionEnabled] = useState(false);