Make the workspace right pane a first-class tab host (#3287)

* feat(app): add persistent workspace side panes

Keep the common review and file-browsing workflow beside the active agent without tearing down pane contents. Workspace tabs now share one compact chip language, assistant file links route into the retained right pane, and diff/file trees share stable geometry.

* fix(app): localize pull request empty state

* test(app): update explorer pane coverage

* fix(app): preserve explorer pane workflows

* test(app): make explorer tab selection idempotent

* fix(app): persist workspace review pins

* fix(app): preserve sidebar scrim drag hook

* fix(app): restore companion pane interactions

* test(app): follow selected sidebar surface

packages/app/src/agent-stream/view.tsx

@@ -445,7 +445,7 @@ const AgentStreamViewComponent = forwardRef<AgentStreamViewHandle, AgentStreamVi
     );
 
     const handleToolCallOpenFile = useStableEvent((filePath: string) => {
-      handleInlinePathPress({ raw: filePath, path: filePath }, "main");
+      handleInlinePathPress({ raw: filePath, path: filePath }, "side");
     });
 
     const handleForkAssistantTurn: AssistantTurnForkHandler = useStableEvent(