Open chat file links at the referenced line (#2309)

* fix(app): open chat file links at referenced lines

Pass chat file locations through the editable CodeMirror path so opening a reference selects and scrolls to its requested line. Cover the real assistant-link flow with a browser regression.

* fix(app): repeat chat file navigation

Track file navigation separately from stable tab identity so reopening the same path and line recenters both editable and read-only panes. Extend the browser regression to cover moving away and clicking the same link again.

* test(app): stabilize repeated file link navigation

packages/app/src/panels/pane-context.tsx

@@ -8,6 +8,7 @@ export interface PaneContextValue {
   workspaceId: string;
   tabId: string;
   target: WorkspaceTabTarget;
+  fileNavigationRevision?: number;
   openTab: (target: WorkspaceTabTarget) => void;
   closeCurrentTab: () => void;
   retargetCurrentTab: (target: WorkspaceTabTarget) => void;