refactor(frontend): the long tail — and eslint-suppressions.json is gone (E27 S2)

Closes the burn-down. Hook suppressions 113 -> 34, `exhaustive-deps` 45 -> 2 (the target was
<10), and every one of the 34 survivors is an inline directive NAMING the invariant it
protects. The suppressions file is deleted, because a bulk file hides the next violation
instead of answering it — and it cannot hold a warning-level rule at all.

The sprint plan's three verdicts missed the answer that turned out to be the most common one:
adjust the state DURING RENDER. React re-runs the component and discards that pass rather than
committing it, so the stale frame an effect-based reset paints does not exist. Applied to the
Plex player's up-next card, the playlist view reset, the feed's optimistic overrides, the
channel banner's retry count, the download center's tab guard, the Plex search highlight, the
comfort-pin latch, Welcome's per-view outcome and the card pager's page clamp. It is legal only
for a component's own state — PlexBrowse's language commit resets PlexProvider's filters, so
that one stays an effect and says why.

Mirrors of a prop or query became derived values or `draft ?? server`:
- `downloadRow` had ui/Avatar's defect exactly — a boolean "poster failed" that an effect reset,
  in rows recycled down a virtualized list, so one job's missing poster painted over the next
  one's for a frame. Keyed by URL now.
- Scheduler's two number editors held a mirror an effect re-synced, on a page that POLLS — the
  shape a poll can overwrite mid-edit. A draft while editing, the server's value otherwise; six
  tests where there were none, the one behavioural change (the save button stops being dirty at
  commit rather than at the echo) mutation-checked.
- SetupWizard's "no token" and WatchPage's "gone" are facts about the URL, so they are seeded and
  derived rather than pushed into state by an effect that had to commit first.

Elsewhere: PlexInfo's rating chip was a component declared during render — a new component type
every render, so React remounted the subtree and dropped the focus on its filter button. Hoisted.
Feed's undo action and PlexPlayer's session reclaim both re-entered their own useCallback, which
the checker reads as a forward reference; both go through the ref idiom this file already uses.
BootGate's dep list was load-bearing for correctness — a re-run meant `location.reload()` — so
the "already adopted THIS identity" comparison now enforces it in code, with a test that fails
without it (the existing reload tests all install their spy too late to catch it).

One correction to the batch before this: keying ChatThread's and Messages' decrypt passes on
`q.data` instead of `q.dataUpdatedAt` was wrong. react-query's structural sharing makes it safe
in production, but the component must not melt down when something hands back a fresh object per
render — and Messages.keyboard.dom.test does exactly that, so the effect span the suite. Both are
back on the fetch as the trigger with the payload behind a ref, which is honest AND loop-proof;
the replaced comment had warned about precisely this.

CLAUDE.md gains four canonical-patterns rows for the above, and its "React 18" line is now true.

frontend/src/components/PersonalViewsModal.tsx

@@ -1,4 +1,4 @@
-import { useEffect, useState } from "react";
+import { useEffect, useRef, useState } from "react";
 import { useTranslation } from "react-i18next";
 import { BookmarkPlus, Check, GripVertical, Play, Save, Star, Trash2, X } from "lucide-react";
 import {
@@ -107,13 +107,16 @@ export default function PersonalViewsModal() {
     },
   });
   const resetDraft = filtersDraft.reset;
+  // Re-seed only when the SELECTION changes, not on every same-view refetch — a refetch returns the
+  // value we just wrote, and re-seeding on it would throw away the prune's undo history. The chosen
+  // view is therefore read through a ref: `selectedId` is the trigger, `selected` is only the data.
+  const selectedRef = useRef(selected);
+  selectedRef.current = selected;
   useEffect(() => {
-    resetDraft(selected?.filters ?? {});
-    setNameDraft(selected?.name ?? "");
-    // Re-seed only when the selection changes (not on every same-view refetch), so pruning keeps its
-    // undo history. Save-current re-seeds explicitly in its own handler.
-    // eslint-disable-next-line react-hooks/exhaustive-deps
-  }, [selectedId]);
+    const view = selectedRef.current;
+    resetDraft(view?.filters ?? {});
+    setNameDraft(view?.name ?? "");
+  }, [selectedId, resetDraft]);
 
   // The selected view's captured filters, as the same human labels its module's chip row shows, read
   // from the undoable draft. The feed hook runs unconditionally (fed empty filters off-feed); Plex