feat(chat): desktop prompt navigator rail (#2054)

* feat(chat): add desktop prompt navigator rail

Add a ChatGPT-style right-center prompt marker rail for web/desktop chat
with hover/keyboard preview panel, load-more for partial history (panel only),
Chat setting, and mod+alt+p shortcut. Disabled in VS Code across rail,
shortcut, settings, help, and search surfaces.

Co-authored-by: Serhii Dziupin <makeittech@users.noreply.github.com>

* fix(ui): read promptNavigatorEnabled from getState in shortcut handler

Match the file convention used by other shortcut handlers so the toggle
does not rely on a hook-level selector closure.

Co-authored-by: Serhii Dziupin <makeittech@users.noreply.github.com>

* fix(ui): drop use-no-memo and default prompt navigator off

Remove the project-unprecedented React Compiler opt-out, and ship the
prompt navigator as opt-in to match other recent chat UI toggles.

Co-authored-by: Serhii Dziupin <makeittech@users.noreply.github.com>

---------

Co-authored-by: Cursor Agent <cursoragent@cursor.com>
Co-authored-by: Serhii Dziupin <makeittech@users.noreply.github.com>

packages/web/server/lib/opencode/settings-helpers.js

@@ -532,6 +532,9 @@ export const createSettingsHelpers = (dependencies) => {
     if (typeof candidate.stickyUserHeader === 'boolean') {
       result.stickyUserHeader = candidate.stickyUserHeader;
     }
+    if (typeof candidate.promptNavigatorEnabled === 'boolean') {
+      result.promptNavigatorEnabled = candidate.promptNavigatorEnabled;
+    }
     if (typeof candidate.expandedEditorToolbar === 'boolean') {
       result.expandedEditorToolbar = candidate.expandedEditorToolbar;
     }