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).

components/setup-dialog.tsx

@@ -36,6 +36,7 @@ import { type ModelCatalogEntry, type ModelSlotName, type ModelsSettings } from
 import { prettyModel } from "@/components/usage-format";
 import { ModelMenuList } from "@/components/settings/model-menu";
 import { MenuShell } from "@/components/menu-shell";
+import { notifySettingsSaved } from "@/components/settings-signal";
 
 /** The pickers' slot identity — same roster language as the Agent
  *  section's slot rows. */
@@ -177,6 +178,7 @@ export function SetupDialog({
 			setError(res ? `Save failed: ${(await res.json().catch(() => ({}))).error ?? res.status}` : "Save failed — network");
 			return;
 		}
+		notifySettingsSaved("models");
 		onDone(models);
 	}