build(frontend): close the lint gaps the E32 audit measured

eslint now also enforces:
- the React Compiler diagnostics that `recommended` leaves out (todo,
  memo-dependencies and ten zero-hit tripwires);
- a description on every suppression, and no blanket disables;
- no focused or skipped tests (vitest and playwright);
- the typed pair no-floating-promises and no-deprecated.

Lint also covers e2e/ and the TypeScript build configs, which `eslint .`
had been skipping in silence.

Every hit is fixed or suppressed inline with a named reason:
- The 31 try statements the compiler cannot lower yet carry a suppression
  until S3 rewrites them. Five other compiler skips were plain fixes:
  a module counter bumped inside a hook, a ref read in a default
  parameter, and a local named like the <section> it renders.
- The real defects behind floating promises are fixed. ChatDock threw at
  nobody when the device key store could not be opened. VideoEditor's
  play() rejection went unhandled. loadYouTubeApi never rejected, so a
  blocked IFrame API left the player on an empty stage forever; it now
  fails on a script error or after 15 s, shows its own error with the
  way out, and lets the next open try again.
- MutableRefObject, FormEvent and lucide's deprecated brand icon are
  replaced. The YouTube glyph now lives in lib/brandIcons.
- The lint-probe harness lets its virtual file names into TypeScript's
  default project, so the contract tests still run the real config.

frontend/src/components/ui/sortableA11y.ts

@@ -65,7 +65,7 @@ export function useSortableA11y(describe: (id: UniqueIdentifier) => SortableSubj
           // dnd-kit reports the item over ITSELF in the pick-up tick (see above), and this flag is
           // the only thing separating that from a real move. A ref would be the wrong lifetime —
           // one drag, not the component.
-          // eslint-disable-next-line react-hooks/immutability
+          // eslint-disable-next-line react-hooks/immutability -- per-DRAG state the announcement closures share; a ref would live as long as the component
           moved = true;
           return t("common.dnd.movedOver", landing(active.id, over.id));
         },