feat(design-system): DS::Disclosure :inline variant + migrate indexa_capital + snaptrade panels (#1715 §6) (#1858)

* feat(design-system): add :inline variant + migrate indexa_capital + snaptrade panels

Adds an `:inline` variant to `DS::Disclosure` for plain text-link-style
toggles that have no surface, no padding, no shadow — the disclosure
reads as a clickable summary text + revealed content, nothing more.

Use case: "Alternative auth" form section toggle in the Indexa Capital
provider panel; "Manage connections" lazy-loaded toggle in the
Snaptrade provider panel. Both were the last raw-`<details>` callsites
in `app/views/settings/providers/`.

Migrations:

- `_indexa_capital_panel.html.erb` — single inline `<details>` revealing
  username / document / password form fields under an "Alternative auth"
  summary text.
- `_snaptrade_panel.html.erb` — lazy-load `<details>` with
  `data-controller="lazy-load"` etc. The new `tag.details ... **opts`
  forwarding from #1857 lets the Stimulus controller attrs flow
  through cleanly via DS::Disclosure's `data:` keyword.

Chevron rotation on snaptrade gets the standard
`motion-safe:transition-transform motion-safe:duration-150` treatment
(was `transition-transform` without the motion-safe gate).

Variant summary now:

| Variant | Details surface | Use case |
|---|---|---|
| `:default` | none / bg-surface summary | inline expander inside parent card |
| `:card` | `bg-container shadow-border-xs rounded-xl p-4` | provider rows, settings sections |
| `:card_inset` | `bg-surface-inset rounded-xl p-4` | inset sub-panels |
| `:inline` | no surface | text-link-style toggles |

* fix(review): guard variant.to_sym against nil in DS::Disclosure

CodeRabbit on #1858 flagged that `variant: nil` crashed with
`NoMethodError` at `variant.to_sym` before the explicit `VARIANTS`
check could run. Use safe navigation (`variant&.to_sym`) so nil
falls through to the validation, and inspect `@variant` in the
error message so nil / non-symbol inputs render readably.

Verified manually via runner: `DS::Disclosure.new(variant: nil)` now
raises `ArgumentError: Invalid variant: nil. Must be one of
[:default, :card, :card_inset, :inline]`.

app/components/DS/disclosure.rb

@@ -1,12 +1,13 @@
 class DS::Disclosure < DesignSystemComponent
   renders_one :summary_content
 
-  VARIANTS = %i[default card card_inset].freeze
+  VARIANTS = %i[default card card_inset inline].freeze
 
   attr_reader :title, :align, :open, :variant, :opts
 
   # `:default` — bg-surface summary, no chrome on the `<details>`. Use
-  # for inline expanders inside a parent card.
+  # for inline expanders that sit inside a parent card (the summary
+  # itself reads as the surface).
   #
   # `:card` — `<details>` itself becomes a `bg-container shadow-border-xs
   # rounded-xl` card; the summary inherits the container (no own bg).
@@ -18,17 +19,23 @@ class DS::Disclosure < DesignSystemComponent
   # (e.g. the IBKR flex-query "report details" panel embedded inside
   # the IBKR settings flow). Same summary contract as `:card`.
   #
-  # In both card variants, callers should pass their own
+  # `:inline` — no surface, no padding, no shadow. The disclosure reads
+  # as a plain text-link-style toggle (e.g. "Alternative auth" inside
+  # a form, or a "Manage connections" lazy-load opener). Caller provides
+  # the summary text (and optional chevron) via the `summary_content`
+  # slot.
+  #
+  # In card / inline variants, callers should pass their own
   # `summary_content` slot; the built-in title rendering assumes the
   # `:default` shape.
   def initialize(title: nil, align: "right", open: false, variant: :default, **opts)
     @title = title
     @align = align.to_sym
     @open = open
-    @variant = variant.to_sym
+    @variant = variant&.to_sym
     @opts = opts
 
-    raise ArgumentError, "Invalid variant: #{@variant}. Must be one of #{VARIANTS.inspect}" unless VARIANTS.include?(@variant)
+    raise ArgumentError, "Invalid variant: #{@variant.inspect}. Must be one of #{VARIANTS.inspect}" unless VARIANTS.include?(@variant)
   end
 
   def details_classes
@@ -59,6 +66,12 @@ class DS::Disclosure < DesignSystemComponent
       # Ring token matches `settings/provider_card.html.erb` (the
       # established focus pattern on container cards).
       "list-none cursor-pointer focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-alpha-black-300 rounded-xl"
+    when :inline
+      # Inline variant: no surface, no padding — the summary reads as
+      # plain text-link copy. Caller markup (text + optional chevron)
+      # provides the visual. Keep cursor + focus-visible ring + matching
+      # alpha-black-300 token used by the card variants for consistency.
+      "list-none cursor-pointer focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-alpha-black-300 rounded-sm"
     else
       "px-3 py-2 rounded-xl cursor-pointer flex items-center justify-between bg-surface focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-alpha-black-300"
     end

app/views/settings/providers/_indexa_capital_panel.html.erb

@@ -29,10 +29,12 @@
                         type: :password %>
     <p class="text-xs text-secondary px-1 -mt-1"><%= t("indexa_capital_items.panel.fields.api_token.description") %></p>
 
-    <details class="group">
+    <%= render DS::Disclosure.new(variant: :inline) do |disclosure| %>
-      <summary class="text-sm text-secondary cursor-pointer hover:text-primary transition-colors">
+      <% disclosure.with_summary_content do %>
-        <%= t("indexa_capital_items.panel.alternative_auth") %>
+        <span class="text-sm text-secondary hover:text-primary transition-colors">
-      </summary>
+          <%= t("indexa_capital_items.panel.alternative_auth") %>
+        </span>
+      <% end %>
       <div class="mt-3 space-y-3 pt-3 border-t border-primary">
         <%= form.text_field :username,
                             label: t("indexa_capital_items.panel.fields.username.label"),
@@ -49,7 +51,7 @@
                             placeholder: is_new_record ? t("indexa_capital_items.panel.fields.password.placeholder_new") : t("indexa_capital_items.panel.fields.password.placeholder_update"),
                             type: :password %>
       </div>
-    </details>
+    <% end %>
 
     <div class="flex justify-end">
       <%= form.submit is_new_record ? t("indexa_capital_items.panel.save_button") : t("indexa_capital_items.panel.update_button"),

app/views/settings/providers/_snaptrade_panel.html.erb

@@ -57,25 +57,31 @@
   <% if items&.any? && items.first.user_registered? %>
     <% item = items.first %>
     <div class="border-t border-primary pt-4 mt-4">
-      <details class="group"
+      <%= render DS::Disclosure.new(
-               data-controller="lazy-load"
+        variant: :inline,
-               data-action="toggle->lazy-load#toggled"
+        data: {
-               data-lazy-load-url-value="<%= connections_snaptrade_item_path(item) %>"
+          controller: "lazy-load",
-               data-lazy-load-auto-open-param-value="manage">
+          action: "toggle->lazy-load#toggled",
-        <summary class="flex items-center justify-between cursor-pointer list-none [&::-webkit-details-marker]:hidden">
+          lazy_load_url_value: connections_snaptrade_item_path(item),
-          <div class="flex items-center gap-2">
+          lazy_load_auto_open_param_value: "manage"
-            <p class="text-sm text-secondary">
+        }
-              <%= t("providers.snaptrade.status_connected", count: item.snaptrade_accounts.count) %>
+      ) do |disclosure| %>
-              <% if item.unlinked_accounts_count > 0 %>
+        <% disclosure.with_summary_content do %>
-                <span class="text-warning">(<%= t("providers.snaptrade.needs_setup", count: item.unlinked_accounts_count) %>)</span>
+          <div class="flex items-center justify-between">
-              <% end %>
+            <div class="flex items-center gap-2">
-            </p>
+              <p class="text-sm text-secondary">
+                <%= t("providers.snaptrade.status_connected", count: item.snaptrade_accounts.count) %>
+                <% if item.unlinked_accounts_count > 0 %>
+                  <span class="text-warning">(<%= t("providers.snaptrade.needs_setup", count: item.unlinked_accounts_count) %>)</span>
+                <% end %>
+              </p>
+            </div>
+            <span class="flex items-center gap-1 text-sm text-secondary hover:text-primary">
+              <%= t("providers.snaptrade.manage_connections") %>
+              <%= icon "chevron-right", class: "w-3 h-3 group-open:rotate-90 motion-safe:transition-transform motion-safe:duration-150" %>
+            </span>
           </div>
-          <span class="flex items-center gap-1 text-sm text-secondary hover:text-primary">
+        <% end %>
-            <%= t("providers.snaptrade.manage_connections") %>
-            <%= icon "chevron-right", class: "w-3 h-3 transition-transform group-open:rotate-90" %>
-          </span>
-        </summary>
 
         <div class="mt-3 space-y-3" data-lazy-load-target="content">
           <div data-lazy-load-target="loading" class="flex items-center gap-2 text-sm text-secondary py-2">
@@ -86,7 +92,7 @@
           <div data-lazy-load-target="frame">
           </div>
         </div>
-      </details>
+      <% end %>
     </div>
   <% end %>
 </div>