chain table: the fenced Delete action + multi-node delete dialog (owner ruling)

"This is really the view deletion should be done in" — the chain table
becomes the graph's MANAGEMENT surface. The floating selection bar
gains Delete FENCED at its right end (owner-approved placement): a
divider quarantines the destructive action from Clear and Generate,
red destructive pair + trash icon, opening the SAME full-death confirm
dialog the canvas uses.

DeleteNodeDialog extended from one node to an array:
- one node renders exactly as always; many pluralize the title
  (Delete N propositions?) and list the names in the mono block,
  capped at 8 + 'and K more'
- the pre-flight impact read aggregates: summed edge counts, unioned
  referencing sessions (deduped, first-seen order); all-404 = gone
- confirm runs the per-node DELETEs SEQUENTIALLY — a failure stops
  the run (extraction_running is never plowed through); onDeleted
  now carries every id that actually died
- the chain table prunes its selection on delete and announces
  lh:graph-revision so the snapshot refetches

Drift fix found en route (surfaced as NaN in the aggregated facts):
the server's NodeDeletionImpact has been {edges, sessions} only since
the quiz-events ledger died in the practice-arc schema slim — the
dialog kept rendering quizEvents/observations as undefined. The dead
fact lines are removed; the dialog now shows exactly what the server
can honestly report.

tests/render-chain-table.test.tsx

@@ -79,6 +79,7 @@ const BASE = {
 	onToggleNodes: () => {},
 	onClear: () => {},
 	onGenerate: () => {},
+	onDelete: () => {},
 	onClose: () => {},
 };
 
@@ -255,13 +256,30 @@ describe("ChainTableBody — the floating selection bar (never shifts layout)",
 		assert.ok(!html.includes('data-testid="chain-selection-bar"'));
 	});
 
-	it("appears with the derived N propositions → M chains + Clear + Generate", () => {
+	it("appears with the derived N propositions → M chains + Clear + Generate + the FENCED Delete", () => {
 		const html = render({ selection: new Set(["a", "b", "c1"]) });
 		assert.ok(html.includes('data-testid="chain-selection-bar"'));
 		assert.ok(html.includes('data-testid="chain-selected-summary"'));
 		assert.ok(html.includes("3 propositions → 1 chain"));
 		assert.ok(html.includes('data-testid="chain-clear"'));
 		assert.ok(html.includes('data-testid="chain-generate"'));
+		// The danger fence (owner, 2026-09-29 night): a divider quarantines
+		// the destructive action at the bar's right end, red + trash icon,
+		// riding the same confirm dialog as the canvas delete.
+		assert.ok(html.includes('data-testid="chain-danger-divider"'));
+		const del = html.match(/<button[^>]*data-testid="chain-delete"[^>]*>/)?.[0] ?? "";
+		assert.match(del, /border-destructive\/50/); // the destructive pair
+		assert.match(del, /aria-label="Delete 3 selected propositions"/);
+		assert.ok(html.includes("lucide-trash-2"), "the trash icon");
+		// the fence is AFTER generate in the DOM (right end of the bar)
+		assert.ok(html.indexOf('chain-generate"') < html.indexOf('chain-danger-divider"'));
+		assert.ok(html.indexOf('chain-danger-divider"') < html.indexOf('chain-delete"'));
+	});
+
+	it("the Delete rides ONLY with a selection — no bar, no kill switch", () => {
+		const html = render({ expandedClusters: new Set(["chat1"]) });
+		assert.ok(!html.includes('data-testid="chain-delete"'));
+		assert.ok(!html.includes('data-testid="chain-danger-divider"'));
 	});
 
 	it("a premise WITHOUT its conclusion derives as the singleton it becomes", () => {