Fix dataset-ref walk false positive and wire spec-mandated success toasts

- Prune the data payload and top-level datasets keys in all three ref walks
  (extractDatasetRefs, renameDatasetInSpec, resolveDatasetRefs) so a data row
  carrying a field named "data" is no longer misread as a library reference,
  spuriously rewritten, or made to throw DatasetNotFoundError. Adds tests,
  including a guard that lookup-transform refs (from.data) still resolve.
- Wire the deferred success toasts now the Toaster has landed: publish, revert,
  extract-to-dataset, and snippet/dataset delete. Copy follows the council
  title-vs-message rule (title states the action, message adds the consequence).
- Reconcile the spec's blanket toast mandate to "toast only what the user can't
  already see": no toast on visible-result creates (snippet, dataset form);
  Copy Reference stays inline and gains an aria-live announcement (new shared
  .visually-hidden utility) instead of a toast-per-copy.
- Move the toast region to bottom-right so it stops covering the header action
  cluster (Publish/Revert, theme/datasets).
- Update docs/spec 01F/02/05 and docs/architecture/07 + 10 to match.

src/app/stores/DatasetStore.ts

@@ -221,6 +221,10 @@ export const useDatasetStore = create<DatasetState>((set, get) => ({
       now,
     });
     get().add(dataset);
+    // Switching to the detail view with the new dataset selected IS the success
+    // confirmation, so no toast is raised — the result is on-screen (spec §05;
+    // docs/architecture/10 → Toast copy). Extract-to-dataset, which creates a
+    // dataset off-screen, does toast (see ExtractStore).
     set({ view: 'detail', form: EMPTY_FORM, formError: null });
     return true;
   },