Add NodeAction: an append-only log of who did what to a nodeHEADmaster

node_id/page_id/user_id are lookup and ordering only -- all three
nullify on delete, so an entry outlives its actor and its subject.
Everything that must survive those deletions lives in a mandatory
metadata jsonb written once at creation: the actor's username, the
node's human-readable name (pinned to the default locale), and
action-specific extras such as publish's title from/to.

NodeAction.record! is the single constructor, so every entry gets
the same baseline metadata without each call site re-implementing
it. occurred_at is one field for live and backfilled entries alike;
inferred_from distinguishes them -- nil means witnessed at the
moment it happened, populated names how a backfilled entry was
estimated.

Instrumented so far: publish (crediting the actual publisher,
threaded through from the controller -- previously nobody had the
act of publishing recorded anywhere), revert's discard_autosave and
destroy_draft branches, and translation destroy. publish_draft! now
runs in a transaction so the promotion and its log entry land
together. The remaining verbs follow once this mechanism has proven
itself.

1 files changed, 19 insertions, 0 deletions

diff --git a/db/migrate/20260714233414_create_node_actions.rb b/db/migrate/20260714233414_create_node_actions.rb
new file mode 100644
index 0000000..6c18285
--- /dev/null
+++ b/db/migrate/20260714233414_create_node_actions.rb
@@ -0,0 +1,19 @@
+class CreateNodeActions < ActiveRecord::Migration[8.1]
+  def change
+    create_table :node_actions do |t|
+      t.references :node, foreign_key: { on_delete: :nullify }
+      t.references :page, foreign_key: { on_delete: :nullify }
+      t.references :user, foreign_key: { on_delete: :nullify }
+      t.string   :action, null: false
+      t.string   :locale
+      t.string   :inferred_from
+      t.jsonb    :metadata, null: false
+      t.datetime :occurred_at, null: false
+
+      t.timestamps
+    end
+
+    add_index :node_actions, [:node_id, :occurred_at]
+    add_index :node_actions, :action
+  end
+end