keyboard: the one-Esc law — a surfaced layer claims at the document level (keyboard 4 of 4)

Owner ruling (keyboard round 2026-10-06): Esc (or any key) does ONE
action, on the topmost active layer. The plan-open-while-dictating
double-act was the symptom: the plan popup listened at WINDOW level
with no claim, and same-node window listeners all fire — the global
chain (registered first) cancelled the dictation while the plan's own
listener closed the plan. One Esc, two actions.

The law (now the house pattern, documented at the chain):
- field-level handlers claim at their element (focus in a field: the
  field's action) — unchanged, already correct
- every SURFACED layer claims at the DOCUMENT level with preventDefault
  + stopPropagation — document fires before the window chain, so the
  chain stays silent under any surface
- the window chain is the bottom-up fallback: dictation (a live capture,
  NOT a surface — it survives the Esc that closes a plan or overlay),
  then abort (escAbortTarget layers its own targets)

Converted to the claim: plan popup, session overlay, chain table,
settings dialog, setup dialog, the delete/abort dialogs (window-level
stopPropagation was never enough — same-node listeners all fire), and
the stats popover. Popovers (popover-dismiss), menus, model picker, and
the sidebar context menu already claimed correctly.

1427 tests, tsc, lint, build green.

components/plan-block.tsx

@@ -639,13 +639,23 @@ export function PlanPopup({ messages, onClose }: { messages: readonly PopupMessa
 	);
 	const statusOf = (id: string): PlanNodeStatus => (statuses ? derivedNodeStatus(statuses, id) : "upcoming");
 
-	// Esc closes.
+	// Esc closes — claimed at the DOCUMENT level (THE ONE-ESC LAW, owner
+	// keyboard round 2026-10-06): a surfaced layer's Esc is exactly one
+	// action. The window-level chain (dictation cancel → abort) is the
+	// fallback for when NOTHING is surfaced; a window listener here could
+	// never stop it — same-node listeners all fire — which was the
+	// plan-open-while-dictating double-act (Esc closed the plan AND
+	// cancelled the dictation).
 	useEffect(() => {
 		const onKey = (e: KeyboardEvent) => {
-			if (e.key === "Escape") onClose();
+			if (e.key === "Escape") {
+				e.preventDefault();
+				e.stopPropagation();
+				onClose();
+			}
 		};
-		window.addEventListener("keydown", onKey);
-		return () => window.removeEventListener("keydown", onKey);
+		document.addEventListener("keydown", onKey);
+		return () => document.removeEventListener("keydown", onKey);
 	}, [onClose]);
 
 	// ── pan/zoom viewport (harvested semantics: fit floor = the default) ──