feat(beta-gating): beta_gated_nav_item helper auto-marks gated entries

Wraps the conditional + dot wiring into a single call so adding a new
beta nav entry doesn't require remembering to set `beta: true` by hand
or duplicating the `beta_features_enabled?` check. Naming mirrors the
existing `BetaGateable` concern.

app/helpers/application_helper.rb

@@ -59,6 +59,16 @@ module ApplicationHelper
     current_page?(path) || (request.path.start_with?(path) && path != "/")
   end
 
+  # Wraps a nav-item hash so a single call performs both halves of a
+  # beta-gated entry: returns `nil` for users without the flag (so the
+  # entry never reaches the rendered nav), and stamps `beta: true` on
+  # the hash for users with the flag (so the partial paints the violet
+  # dot on the icon). Use inside an `Array#compact` nav-items list.
+  def beta_gated_nav_item(item)
+    return nil unless beta_features_enabled?
+    item.merge(beta: true)
+  end
+
   # Wrapper around I18n.l to support custom date formats
   def format_date(object, format = :default, options = {})
     date = object.to_date

app/views/layouts/application.html.erb

@@ -11,7 +11,7 @@ else
     { name: t(".nav.transactions"), path: transactions_path, icon: "credit-card", icon_custom: false, active: page_active?(transactions_path) },
     { name: t(".nav.reports"), path: reports_path, icon: "chart-bar", icon_custom: false, active: page_active?(reports_path) },
     { name: t(".nav.budgets"), path: budgets_path, icon: "map", icon_custom: false, active: page_active?(budgets_path) },
-    (beta_features_enabled? ? { name: t(".nav.goals"), path: goals_path, icon: "piggy-bank", icon_custom: false, active: page_active?(goals_path), beta: true } : nil),
+    beta_gated_nav_item({ name: t(".nav.goals"), path: goals_path, icon: "piggy-bank", icon_custom: false, active: page_active?(goals_path) }),
     { name: t(".nav.assistant"), path: chats_path, icon: "icon-assistant", icon_custom: true, active: page_active?(chats_path), mobile_only: true }
   ].compact
 end %>

docs/llm-guides/gating-a-beta-feature.md

@@ -61,18 +61,18 @@ Same pattern works for dashboard widgets, scoreboard cards, anything that surfac
 
 The desktop sidebar rail and the mobile bottom nav both render from `app/views/layouts/shared/_nav_item.html.erb`. The partial accepts an optional `beta:` local — when true, it overlays a violet dot-only pill on the icon so opted-in users can tell at a glance that the rail entry leads to a beta surface.
 
-Build the nav-item hash conditionally inside the `beta_features_enabled?` branch and set `beta: true` on it. The compact form using `Array#compact` keeps the array clean:
+Use the `beta_gated_nav_item` helper to wrap the entry. It returns `nil` for non-beta users (so the entry never enters the nav, once `Array#compact` runs) and stamps `beta: true` for opted-in users (so the partial paints the dot). One call, both halves of the gate:
 
 ```erb
 <% mobile_nav_items = [
   { name: t(".nav.home"), path: root_path, icon: "pie-chart", icon_custom: false, active: page_active?(root_path) },
   { name: t(".nav.transactions"), path: transactions_path, icon: "credit-card", icon_custom: false, active: page_active?(transactions_path) },
-  (beta_features_enabled? ? { name: t(".nav.goals"), path: goals_path, icon: "piggy-bank", icon_custom: false, active: page_active?(goals_path), beta: true } : nil),
+  beta_gated_nav_item({ name: t(".nav.goals"), path: goals_path, icon: "piggy-bank", icon_custom: false, active: page_active?(goals_path) }),
   { name: t(".nav.assistant"), path: chats_path, icon: "icon-assistant", icon_custom: true, active: page_active?(chats_path), mobile_only: true }
 ].compact %>
 ```
 
-Two things happen from this single change: non-beta users never see the entry (the `nil` gets compacted out) and beta users see the entry with the dot marker (the partial reads `beta:` and renders the pill). You don't need to touch `_nav_item.html.erb` itself.
+You don't need to touch `_nav_item.html.erb` or set `beta: true` by hand. Adding a new beta nav entry is one helper call wrapped around the same hash you'd write anyway.
 
 ## Marking the feature in the UI
 
@@ -131,7 +131,7 @@ When a feature moves from beta to general availability, removing the gate is a s
 
 1. Drop the `before_action :require_beta_features!` line from the controller.
 2. Unwrap the `if beta_features_enabled?` blocks in views.
-3. Drop the `DS::Pill` markers from headers and section titles, and drop the `beta: true` flag from the nav-item hash.
+3. Drop the `DS::Pill` markers from headers and section titles, and unwrap the `beta_gated_nav_item(...)` call back into a plain nav-item hash.
 4. Delete the controller / view tests that exercise the redirect.
 
 Grep for `require_beta_features!` and `beta_features_enabled?` near your feature to confirm nothing's left behind.