Fix wave chunk 1: cross-surface settings signal, dialog scroll-lock, noneRow retired

- lh:settings-saved CustomEvent (the lh:chat-renamed pattern, owner
  ruling): every writer (composer save, SetupDialog save, the settings
  write seam — one dispatch point carrying the section) notifies after a
  successful PUT; every reader re-reads its own seam: ModelControl's
  record read, the Agent section's slots/catalog, and chat.tsx's
  configured state (clearing slots mid-session now surfaces the setup
  CTA without a reload). Self-notifications re-read idempotently.
- MenuShell now announces lh:menu-open/lh:menu-close (still placement-
  only); the settings dialog's content column locks (overflow-hidden,
  count-based) while any menu is open — wheel-scrolling with a dropdown
  down is dead; the re-place-on-scroll fallback stays for un-lockable
  surfaces.
- The settings thinking menus' 'Default' noneRow is retired (owner:
  the unset state can't re-enter once chunk 2's auto-populate lands; no
  unpin is needed).
- Live-caught regression from the MenuShell migration fixed: the
  composer's outside-click handler never learned the portaled menu body
  isn't a container descendant — menu-row pointerdowns counted as
  outside and ATE THE PICK (composer picks have been dead for pointer
  users since 221c99d); rows now carve out via [data-lh-menu], the
  settings sections' discipline.
- Item 4 (resolved-level display for legacy records) deferred to chunk 2
  per owner ruling — the payload omits the level for legacy no-level
  records and DEFAULT_THINKING_ORDER was server-only (now in the core
  barrel via bd68486, exactly the seam chunk 2 needs).

tests/settings-signal.test.ts

@@ -0,0 +1,67 @@
+/**
+ * The cross-surface settings signal (fix wave, owner ruling 2026-09-22):
+ * writers dispatch lh:settings-saved {section} after a successful PUT,
+ * readers re-read. These tests pin the SEAM's contract — delivery,
+ * section detail, unsubscribe, and junk-event tolerance — against a bare
+ * EventTarget standing in for window (Node has no DOM; the reader WIRING
+ * is verified live per dev-verification.md).
+ */
+import assert from "node:assert/strict";
+import { afterEach, describe, it } from "node:test";
+
+// A DOM-less window: EventTarget is all the seam touches. The module
+// imports react (harmless) and reads window at CALL time, not import time.
+const realWindow = (globalThis as { window?: unknown }).window;
+(globalThis as { window: unknown }).window = new EventTarget();
+
+const {
+	SETTINGS_SAVED_EVENT,
+	notifySettingsSaved,
+	onSettingsSaved,
+} = await import("../components/settings-signal.ts");
+
+afterEach(() => {
+	(globalThis as { window: unknown }).window = realWindow ?? new EventTarget();
+});
+
+describe("settings-signal — the seam's contract", () => {
+	it("a writer's notify reaches a reader with the section", () => {
+		const got: string[] = [];
+		const off = onSettingsSaved((section) => got.push(section));
+		notifySettingsSaved("models");
+		assert.deepEqual(got, ["models"]);
+		off();
+	});
+
+	it("unsubscribe stops delivery (a reader unmounting never leaks)", () => {
+		const got: string[] = [];
+		const off = onSettingsSaved((section) => got.push(section));
+		off();
+		notifySettingsSaved("models");
+		assert.deepEqual(got, []);
+	});
+
+	it("readers filter their own section — general doesn't reach a models reader", () => {
+		const got: string[] = [];
+		const off = onSettingsSaved((s) => {
+			if (s === "models") got.push(s);
+		});
+		notifySettingsSaved("general");
+		notifySettingsSaved("appearance");
+		assert.deepEqual(got, []);
+		notifySettingsSaved("models");
+		assert.deepEqual(got, ["models"]);
+		off();
+	});
+
+	it("a foreign CustomEvent on the same name with no section detail is ignored", () => {
+		const got: string[] = [];
+		const off = onSettingsSaved((section) => got.push(section));
+		// e.g. some other dispatch path that forgot the detail payload
+		globalThis.window.dispatchEvent(
+			new CustomEvent(SETTINGS_SAVED_EVENT, { detail: undefined }),
+		);
+		assert.deepEqual(got, []);
+		off();
+	});
+});