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/ui/src/lib/i18n/messages/en.settings.ts

@@ -1059,6 +1059,7 @@ export const settingsDict = {
   'settings.openchamber.keyboardShortcuts.action.open_model_selector.label': 'Open model selector',
   'settings.openchamber.keyboardShortcuts.action.expand_input.label': 'Expand input',
   'settings.openchamber.keyboardShortcuts.action.open_timeline_dialog.label': 'Open conversation timeline',
+  'settings.openchamber.keyboardShortcuts.action.toggle_prompt_navigator.label': 'Toggle prompt navigator',
   'settings.projects.sidebar.total': 'Total {count}',
   'settings.projects.sidebar.actions.addProject': 'Add project',
   'settings.projects.page.empty.noProjects': 'No projects available.',
@@ -1803,6 +1804,8 @@ export const settingsDict = {
   'settings.openchamber.visual.field.collapsibleUserMessages': 'Collapse Long User Messages',
   'settings.openchamber.visual.field.stickyUserHeaderAria': 'Sticky user header',
   'settings.openchamber.visual.field.stickyUserHeader': 'Sticky User Header',
+  'settings.openchamber.visual.field.promptNavigatorEnabledAria': 'Prompt navigator',
+  'settings.openchamber.visual.field.promptNavigatorEnabled': 'Prompt Navigator',
   'settings.openchamber.visual.field.expandedEditorToolbarAria': 'Always show editor toolbar',
   'settings.openchamber.visual.field.expandedEditorToolbar': 'Always show editor toolbar (docked under the file tabs)',
   'settings.openchamber.visual.field.wideChatLayoutAria': 'Wide chat layout',