Fix ConfirmButton Enter/Space keydown bubbling to parent row handler

The button's onClick stopped mouse event propagation, but keyboard
Enter/Space fired a separate keydown event that bubbled to the
combatant row's onKeyDown, opening the stat block side panel instead
of arming/confirming the button.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

apps/web/src/__tests__/confirm-button.test.tsx

@@ -195,4 +195,24 @@ describe("ConfirmButton", () => {
 		fireEvent.blur(button);
 		expect(screen.getByTestId("x-icon")).toBeTruthy();
 	});
+
+	it("Enter/Space keydown stops propagation to prevent parent handlers", () => {
+		const parentHandler = vi.fn();
+		render(
+			// biome-ignore lint/a11y/noStaticElementInteractions: test wrapper
+			<div onKeyDown={parentHandler}>
+				<ConfirmButton
+					icon={<XIcon />}
+					label="Remove combatant"
+					onConfirm={vi.fn()}
+				/>
+			</div>,
+		);
+		const button = screen.getByRole("button");
+
+		fireEvent.keyDown(button, { key: "Enter" });
+		fireEvent.keyDown(button, { key: " " });
+
+		expect(parentHandler).not.toHaveBeenCalled();
+	});
 });