fix(channels,datatable): address R13 S2a review + unify tag chips with the Tags column filter

Review fixes (user /code-review high):
- DataTable: hoist a stable EMPTY_FILTERS fallback so a controlled caller that omits
  `filters` doesn't churn a fresh {} each render.
- DataTable: the persistKey blob now stores only the slices this table OWNS — a
  controlled sort/filter is written as null/{} instead of a stale never-read duplicate.
- useFilterState: optional `migrate` seed (used only when storage is empty);
  ChannelsProvider carries the retired LS.channelFilter sync chip forward via migrateSyncChip.
- Channels: guard the sync-chip read with typeof instead of an `as string` cast.

Also unify the tag filter, same as the sync one: the top "YOUR TAGS" chip row is now a
controlled view over the Tags COLUMN filter (`filters.tags`), replacing its own tagFilter
state — so the chips and the Tags funnel share one state bidirectionally, the card layout
applies it via filterRows, and it persists with the rest of the map.

frontend/src/components/DataTable.tsx

@@ -25,6 +25,11 @@ interface Persisted {
   size?: number;
 }
 
+// Stable empty-map identity for the controlled-but-value-omitted fallback, so `filters` keeps a
+// constant reference across renders (a fresh `{}` would churn the persist effect + re-filter every
+// render). Mirrors controlled sort's stable `null` fallback.
+const EMPTY_FILTERS: FilterMap = {};
+
 function loadPersist(key?: string): Persisted {
   const empty: Persisted = { sort: null, filters: {}, page: 0 };
   if (!key) return empty;
@@ -103,7 +108,7 @@ export default function DataTable<T>({
   // otherwise the table keeps its own, seeded from and saved to persistKey — symmetric to sort.
   const controlledFilters = onFiltersChange !== undefined;
   const [internalFilters, setInternalFilters] = useState<FilterMap>(initial.filters);
-  const filters = controlledFilters ? (filtersProp ?? {}) : internalFilters;
+  const filters = controlledFilters ? (filtersProp ?? EMPTY_FILTERS) : internalFilters;
   const [page, setPage] = useState(initial.page);
   const [size, setSize] = useState(initial.size ?? pageSize);
 
@@ -117,9 +122,20 @@ export default function DataTable<T>({
     else setInternalFilters(next);
   };
 
+  // Persist page/size always, but only the sort/filter slices this table actually OWNS — a controlled
+  // caller persists those itself, so writing them here would just leave a stale, never-read duplicate.
   useEffect(() => {
-    if (persistKey) localStorage.setItem(persistKey, JSON.stringify({ sort, filters, page, size }));
-  }, [persistKey, sort, filters, page, size]);
+    if (!persistKey) return;
+    localStorage.setItem(
+      persistKey,
+      JSON.stringify({
+        sort: controlledSort ? null : sort,
+        filters: controlledFilters ? {} : filters,
+        page,
+        size,
+      }),
+    );
+  }, [persistKey, controlledSort, controlledFilters, sort, filters, page, size]);
 
   useEffect(() => {
     if (!externalFilter) return;