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/components/DatasetsModal.tsx

@@ -191,8 +191,16 @@ function DatasetDetail({
       confirmLabel: 'Delete',
       danger: true,
     });
-    // TODO (M6, spec §05): success toast on delete.
-    if (ok) remove(dataset.id);
+    if (!ok) return;
+    const removedName = dataset.name;
+    remove(dataset.id);
+    // Confirm the deletion (spec §05). The message names which dataset went
+    // (council toast-copy rule, docs/architecture/10 → Toast copy).
+    notify({
+      kind: 'success',
+      title: 'Dataset deleted',
+      message: `"${removedName}" was permanently removed.`,
+    });
   };
 
   return (
@@ -203,6 +211,13 @@ function DatasetDetail({
           <button type="button" className={styles.action} onClick={() => void handleCopy()}>
             {copied ? 'Copied' : 'Copy Reference'}
           </button>
+          {/* The clipboard write is invisible, so the success is confirmed inline
+              ("Copied") rather than by a toast (docs/architecture/10 → Toast copy).
+              This polite live region announces it to assistive tech, which the
+              button's visual label swap alone would not reliably do. */}
+          <span role="status" className="visually-hidden">
+            {copied ? 'Reference copied to clipboard' : ''}
+          </span>
           <button type="button" className={styles.action} onClick={handleEdit}>
             Edit
           </button>

src/app/components/SnippetLibrary.tsx

@@ -11,6 +11,7 @@
 import { useShallow } from 'zustand/react/shallow';
 import { formatSnippetSize, hasUnpublishedChanges, snippetSizeBytes } from '@core/snippet';
 import { confirm } from '../stores/ConfirmStore';
+import { notify } from '../stores/NotificationStore';
 import { useSnippetStore } from '../stores/SnippetStore';
 import styles from './SnippetLibrary.module.css';
 
@@ -73,18 +74,28 @@ export function SnippetLibrary() {
 
   const handleDelete = async (id: string, name: string) => {
     // In-app confirmation (docs/architecture/03 → confirmation dialogs).
-    // TODO: surface a deletion toast (spec §02) once the toast system lands (M6).
     const ok = await confirm({
       title: 'Delete snippet',
       message: `Delete "${name}"? This cannot be undone.`,
       confirmLabel: 'Delete',
       danger: true,
     });
-    if (ok) removeSnippet(id);
+    if (!ok) return;
+    removeSnippet(id);
+    // Confirm the deletion (spec §02). The message names which snippet went —
+    // useful when toasts stack (council toast-copy rule, docs/architecture/10).
+    notify({
+      kind: 'success',
+      title: 'Snippet deleted',
+      message: `"${name}" was permanently removed from your library.`,
+    });
   };
 
   return (
     <div className={styles.library}>
+      {/* Create raises no toast: the new snippet opens in the editor, so the
+          result is already on-screen (spec §02; docs/architecture/10 → Toast
+          copy). Delete/duplicate toast because the outcome isn't visible. */}
       <button className={styles.createNew} onClick={() => createSnippet()}>
         + Create New Snippet
       </button>

src/app/components/SpecEditor.tsx

@@ -27,6 +27,7 @@ import { openModal } from '../modals/ModalCoordinator';
 import { useAppStore } from '../stores/AppStore';
 import { confirm } from '../stores/ConfirmStore';
 import { hasInlineData } from '../stores/ExtractStore';
+import { notify } from '../stores/NotificationStore';
 import { usePreviewStore } from '../stores/PreviewStore';
 import { selectActiveSnippet, selectShownText, useSnippetStore } from '../stores/SnippetStore';
 import { SegmentedControl, type SegmentedOption } from './SegmentedControl';
@@ -64,7 +65,14 @@ function EditorToolbar() {
   const handlePublish = () => {
     if (!useSnippetStore.getState().activeSnippetId) return;
     useSnippetStore.getState().publish();
-    // TODO: success toast "Snippet published" once the toast system lands (M6, spec §03D).
+    // Success confirmation (spec §03D). Per the council's toast-copy rule
+    // (docs/architecture/10 → Toast copy), the title states the action and the
+    // message adds the consequence rather than paraphrasing it.
+    notify({
+      kind: 'success',
+      title: 'Snippet published',
+      message: 'Your draft is now the published version.',
+    });
   };
 
   const handleRevert = async () => {
@@ -77,7 +85,11 @@ function EditorToolbar() {
     });
     if (ok) {
       useSnippetStore.getState().revert();
-      // TODO: success toast "Draft reverted" once the toast system lands (M6, spec §03D).
+      notify({
+        kind: 'success',
+        title: 'Draft reverted',
+        message: 'The editor was restored to the last published version.',
+      });
     }
   };
 

src/app/components/Toaster.module.css

@@ -1,10 +1,14 @@
 .region {
   position: fixed;
-  top: var(--space-5);
+  /* Bottom-right, not top-right: the header's action cluster (Publish/Revert,
+     theme/datasets controls) lives top-right, and a toast there lands on top of
+     the control the user just used. Bottom-anchored, the stack grows upward and
+     the newest toast sits nearest the corner (docs/architecture/10 → Toasts). */
+  bottom: var(--space-5);
   right: var(--space-5);
   /* Above the confirm backdrop (z 1000) so a failure stays visible and
-     dismissible even with a confirmation open; top-right won't block the
-     centered dialog. */
+     dismissible even with a confirmation open; the corner clears the centered
+     dialog. */
   z-index: 1100;
   display: flex;
   flex-direction: column;

src/app/components/Toaster.tsx

@@ -2,8 +2,9 @@
  * Toaster — renders the NotificationStore as a stack of toasts (spec §10,
  * design language → Toasts). Mounted once at the app root, beside ConfirmDialog.
  *
- * The non-blocking counterpart to ConfirmDialog: top-right, stacked newest-last,
- * each dismissible. Error/warning toasts persist until dismissed (Carbon: a
+ * The non-blocking counterpart to ConfirmDialog: bottom-right, stacked
+ * newest-nearest-the-corner, each dismissible (placement rationale in
+ * Toaster.module.css). Error/warning toasts persist until dismissed (Carbon: a
  * critical message shouldn't vanish on a timer); success/info auto-dismiss. A
  * failure that carries diagnostic `detail` exposes it under a collapsed
  * "Technical details" disclosure — available to report, without shouting.

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;
   },

src/app/stores/ExtractStore.ts

@@ -17,6 +17,7 @@ import type { DataFormat } from '@core/format-detection';
 import { createDataset } from '@core/dataset';
 import { isNameTaken } from '@core/naming';
 import { useDatasetStore } from './DatasetStore';
+import { notify } from './NotificationStore';
 import { useSnippetStore } from './SnippetStore';
 
 /** The inline `data` block of a parsed spec, if it carries `values`. */
@@ -123,8 +124,14 @@ export const useExtractStore = create<ExtractState>((set, get) => ({
     spec.data = { name };
     useSnippetStore.getState().replaceActiveDraft(JSON.stringify(spec, null, 2), now);
 
-    // TODO (M6, spec §03F): success toast "Dataset created" — deferred with the
-    // other success toasts (see SnippetStore publish/revert breadcrumbs).
+    // Success confirmation (spec §03F). Title states the action; the message
+    // adds the consequence — the spec was rewritten to reference the new dataset
+    // by name (council toast-copy rule, docs/architecture/10 → Toast copy).
+    notify({
+      kind: 'success',
+      title: 'Dataset created',
+      message: `The spec now references "${name}" instead of its inline data.`,
+    });
     set(INITIAL);
     return true;
   },