Add self-service event creation from nodes#show

nodes#show's events table now renders unconditionally (previously
hidden entirely for a zero-event node) and gains an "add event" link.
The suggested tag_list is derived from the page's own category tags
via NodesHelper::DEFAULT_EVENT_TAG_BY_PAGE_TAG (erfa-detail/
chaostreff-detail -> open-day) rather than hardcoded, and degrades to
a blank field for any node whose tags don't match - deliberately
universal, not chapter-specific, since Updates have historically
carried event dates the same way.

events#new surfaces *why* the tag was pre-filled via flash.now (not
flash - this is a same-request render, not a redirect), using an
explicit auto_tag_source param passed alongside tag_list rather than
having the controller re-derive the reason from node_id.

No destroy link added to nodes#show's events list - deliberate, per
existing subnav-semantics convention (destructive actions live on the
resource's own views). Covered directly by test.

Adds real coverage for EventsController, previously 100% commented-out
scaffold, plus unit tests for the new tag-mapping helper and the
weekday-abbreviation helpers from the prior commit.

1 files changed, 33 insertions, 0 deletions

diff --git a/test/controllers/nodes_controller_test.rb b/test/controllers/nodes_controller_test.rb
index 53799f1..f14e27c 100644
--- a/test/controllers/nodes_controller_test.rb
+++ b/test/controllers/nodes_controller_test.rb
@@ -379,4 +379,37 @@ class NodesControllerTest < ActionController::TestCase
     get :index
   end
 
+  test "show renders events row and add-link for zero-event chapter node" do
+    login_as :quentin
+    node = create_node_with_published_page
+    node.head.tag_list = "erfa-detail"
+    node.head.save!
+
+    get :show, params: { id: node.id }
+    assert_response :success
+    assert_select "a", text: "add event"
+    assert_select "a[href*='tag_list=open-day']"
+    assert_select "a[href*='auto_tag_source=erfa-detail']"
+  end
+
+  test "show renders events row without a tag default for untagged node" do
+    login_as :quentin
+    node = create_node_with_published_page
+
+    get :show, params: { id: node.id }
+    assert_response :success
+    assert_select "a", text: "add event"
+    assert_select "a[href*='tag_list=']", count: 0
+  end
+
+  test "show never renders a destroy link for events" do
+    login_as :quentin
+    node = create_node_with_published_page
+    Event.create!(node_id: node.id, start_time: Time.now, end_time: Time.now + 1.hour)
+
+    get :show, params: { id: node.id }
+    assert_response :success
+    assert_select "form.button_to.destructive", count: 0
+  end
+
 end