feat(marketing-pages): subscribe to auth.user.signed-up

Generated handler + Payload event-task via gen event consume,
threaded through symbols / both binders / cms re-export at the
configured anchors. bus.subscribe wires the in-memory delivery in
dev-seed; the __events.auth.user.signed-up.marketing-pages Payload
task closes the production-bus loop.

Also fixes two generator-level issues found during Phase 8:
- Drop publisher prompt's `when` clause so --args can supply the
  4th positional argument (Plop limitation: --args cannot bypass
  conditional prompts). Validate runs only in consume mode.
- Switch event-task.ts.hbs from TaskConfig<"slug-string"> to
  TaskConfig<{ input: ...; output: object }> since runtime-generated
  event slugs are not keys of TypedJobs['tasks'].

turbo/generators/config.ts

@@ -378,11 +378,12 @@ export default function generator(plop: PlopTypes.NodePlopAPI): void {
       {
         type: "input",
         name: "publisher",
-        message: "Publisher feature (kebab-case; only for consume mode):",
-        when(answers: { mode: string }) {
-          return answers.mode === "consume";
-        },
-        validate(input: string, answers: { event: string }) {
+        message:
+          "Publisher feature (kebab-case; required for consume, ignored for publish):",
+        // Always shown — `--args` cannot bypass conditional prompts (Plop limitation).
+        // Publish mode accepts any value (it's ignored by publishActions).
+        validate(input: string, answers: { mode: string; event: string }) {
+          if (answers.mode === "publish") return true;
           if (!/^[a-z][a-z0-9-]*$/.test(input)) return "Must be kebab-case";
           const eventKebab = answers.event.replace(/\./g, "-");
           const path = join(