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/lib/plexPlayerHooks.ts

@@ -3,7 +3,6 @@ import {
   useEffect,
   useRef,
   useState,
-  type MutableRefObject,
   type RefObject,
   type WheelEvent as ReactWheelEvent,
 } from "react";
@@ -113,16 +112,23 @@ export function useControlsVisibility(opts: {
     if (hideTimer.current) window.clearTimeout(hideTimer.current);
     if (!barAutoHideRef.current) return; // per-user setting: never auto-hide the control bar
     const wokeAt = Date.now();
-    const arm = (ms: number) => {
-      hideTimer.current = window.setTimeout(() => {
-        // Keep the controls up while the audio/subtitle menu is open, else it would vanish mid-choice.
-        if (videoRef.current?.paused || menuOpenRef.current || hovered.current) return;
-        const held = FOCUS_HOLD_MS - (Date.now() - wokeAt);
-        if (focused.current && held > 0) return arm(held);
-        setVisible(false);
-      }, ms);
-    };
-    arm(HIDE_MS);
+    // Keep the controls up while the audio/subtitle menu is open, else it would vanish mid-choice.
+    const busy = () => !!videoRef.current?.paused || menuOpenRef.current || hovered.current;
+    // Not a timer that re-arms itself: a self-calling `arm` read to the compiler's analysis as a
+    // value from outside this callback (memo-dependencies), and a self-naming function expression
+    // tripped one of its invariants. The focus hold re-arms at most once — the second timer fires
+    // when the hold is over, so it has only `busy` left to ask.
+    hideTimer.current = window.setTimeout(() => {
+      if (busy()) return;
+      const held = FOCUS_HOLD_MS - (Date.now() - wokeAt);
+      if (focused.current && held > 0) {
+        hideTimer.current = window.setTimeout(() => {
+          if (!busy()) setVisible(false);
+        }, held);
+        return;
+      }
+      setVisible(false);
+    }, HIDE_MS);
   }, [barAutoHideRef, menuOpenRef, videoRef, setVisible]);
   const show = useCallback(
     (visible: boolean) => {
@@ -188,8 +194,8 @@ export function usePlexProgress(opts: {
   id: string;
   qc: QueryClient;
   videoRef: RefObject<HTMLVideoElement | null>;
-  absRef: MutableRefObject<number>;
-  durationRef: MutableRefObject<number>;
+  absRef: RefObject<number>;
+  durationRef: RefObject<number>;
 }): { settle: () => void; finish: (confirmed?: Promise<unknown>) => void } {
   const { id, qc, videoRef, absRef, durationRef } = opts;
   const settleRef = useRef<() => void>(() => {});
@@ -341,10 +347,7 @@ export function usePlexProgress(opts: {
  *  answer is where the session was ASKED to start. Anything that restarts the session "here" — an
  *  audio switch, an A/V offset, a keyboard seek — must use this: reading `abs` restarted a resume at
  *  20:00 from 0:00, and the next checkpoint saved that (deep-review round 4). */
-export function playhead(
-  absRef: MutableRefObject<number>,
-  loadStartRef: MutableRefObject<number>,
-): number {
+export function playhead(absRef: RefObject<number>, loadStartRef: RefObject<number>): number {
   return absRef.current > 0 ? absRef.current : loadStartRef.current;
 }
 
@@ -439,8 +442,8 @@ export function useAutoSkip(opts: {
 }): {
   activeMarker: PlexMarker | undefined;
   skipProgress: number | null;
-  skipProgressRef: MutableRefObject<number | null>;
-  cancelAutoSkipRef: MutableRefObject<() => void>;
+  skipProgressRef: RefObject<number | null>;
+  cancelAutoSkipRef: RefObject<() => void>;
   doSkip: (m: PlexMarker) => void;
 } {
   const {
@@ -594,12 +597,12 @@ export function usePlexTracks(opts: {
   videoRef: RefObject<HTMLVideoElement | null>;
   hlsRef: RefObject<Hls | null>;
   multiAudioRef: RefObject<boolean>;
-  audioRef: MutableRefObject<number | null>;
-  aoffRef: MutableRefObject<number>;
-  absRef: MutableRefObject<number>;
+  audioRef: RefObject<number | null>;
+  aoffRef: RefObject<number>;
+  absRef: RefObject<number>;
   /** The position the current (or still in-flight) session was ASKED to start at — written before
    *  the session request goes out, unlike `sessionK`, which only lands once it has answered. */
-  loadStartRef: MutableRefObject<number>;
+  loadStartRef: RefObject<number>;
 }): {
   audioOrd: number | null;
   setAudioOrd: (ord: number | null) => void;
@@ -677,7 +680,7 @@ export function usePlexTracks(opts: {
         }
       } else {
         // Single audio (or the session has not answered yet): re-map the track server-side.
-        loadSession(playhead(absRef, loadStartRef));
+        void loadSession(playhead(absRef, loadStartRef));
       }
     },
     [loadSession, detail, patchPrefs, audioRef, multiAudioRef, hlsRef, absRef, loadStartRef],