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/AddToPlaylist.tsx

@@ -2,7 +2,8 @@ import { useLayoutEffect, useState } from "react";
 import { useTranslation } from "react-i18next";
 import { useQuery, useQueryClient } from "@tanstack/react-query";
 import { qk } from "../lib/queryKeys";
-import { ListPlus, Plus, Youtube } from "lucide-react";
+import { ListPlus, Plus } from "lucide-react";
+import { YouTubeIcon } from "../lib/brandIcons";
 import { MenuCheck } from "./ui/MenuCheck";
 import { api, type Playlist } from "../lib/api";
 import { notifyActionError } from "../lib/actionErrors";
@@ -117,6 +118,7 @@ function MembershipPanel({
   async function toggle(pl: Playlist) {
     if (busy) return;
     setBusy(true);
+    // eslint-disable-next-line react-hooks/todo -- the React Compiler cannot lower try/finally yet, so the enclosing component or hook stays uncompiled; pinned in compilerCoverage, burned down in E32 S3
     try {
       if (pl.has_video) await api.removeFromPlaylist(pl.id, videoId);
       else await api.addToPlaylist(pl.id, videoId);
@@ -132,6 +134,7 @@ function MembershipPanel({
     const name = newName.trim();
     if (!name || busy) return;
     setBusy(true);
+    // eslint-disable-next-line react-hooks/todo -- the React Compiler cannot lower try/finally yet, so the enclosing component or hook stays uncompiled; pinned in compilerCoverage, burned down in E32 S3
     try {
       const pl = await api.createPlaylist(name);
       await api.addToPlaylist(pl.id, videoId);
@@ -183,7 +186,7 @@ function MembershipPanel({
                 <MenuCheck kind="many" on={!!pl.has_video} />
                 <span className="truncate flex-1 text-left">{playlistName(pl, t)}</span>
                 {(pl.source === "youtube" || pl.yt_playlist_id) && (
-                  <Youtube className="w-3 h-3 shrink-0 text-muted" />
+                  <YouTubeIcon className="w-3 h-3 shrink-0 text-muted" />
                 )}
               </PopoverItem>
             ))}