The global Escape arbiter in ui.js only sees `.modal` elements, so the many
ad-hoc dropdowns and context popups that are built on the fly and appended to
<body> ignored Escape entirely: document-library card/chat menus, chat
context/stats/overflow popups, cookbook serve & running menus, calendar event
menus, and compare pane menus.
Add a small DOM-free dismissal registry (static/js/escMenuStack.js). Menus
register a dismiss callback while open, and the arbiter closes the
most-recently-opened one first, so a menu opened over a modal closes before the
modal. bindMenuDismiss() wires the ubiquitous "append-to-body, close on outside
click" idiom to both the outside-click listener and the Escape stack in one
call, and dismissOrRemove() lets the pre-existing bulk removers (scroll/swipe/
modal-dismiss cleanup, reopen sweeps) tear a menu down through its real teardown
instead of orphaning its stack entry.
Covers ~14 menus across documentLibrary, chatRenderer, cookbookServe,
cookbookRunning, calendar, and compare/panes. Every teardown path — item click,
outside click, swipe, toggle, rebuild, bulk cleanup — routes through the
registry so no entry is ever stranded.
tests/test_esc_menu_stack_js.py pins the registry's LIFO and
exactly-one-per-press guarantees (node-driven; skips when node is absent).
