feat(channels): suggest your own tags for untagged channels from your tagging pattern (E8·S4)

Learn, per user tag, which auto TOPIC tags are characteristic of the channels
you've tagged it, then suggest that tag for still-untagged subscribed channels
whose topics cover enough of the profile. Language auto-tags are excluded from
the signal — near-universal within a language, they flooded every channel.

New GET /api/tags/suggestions (read-only, deterministic) backed by
app/sync/tagsuggest.py. Surfaced in the Channel Manager as dashed "ghost" chips
in the tags cell — one tap accepts (reuses the attach-tag endpoint), × dismisses
for the session — plus a header badge and a bulk "Accept N confident" (the
full-profile matches) behind a confirm. No silent writes (D4 = suggest-and-confirm).

Also reflow a pre-existing prettier drift in dateFilter.ts from E8·S2.

frontend/src/components/channelColumns.tsx

@@ -9,7 +9,7 @@ import Tooltip from "./Tooltip";
 import { PriorityStepper } from "./PriorityStepper";
 import ChannelLink from "./ChannelLink";
 import AboutCell from "./AboutCell";
-import { ChannelTagsControl } from "./ChannelTags";
+import { ChannelTagsControl, type SuggestedTag } from "./ChannelTags";
 
 /** The shared "subscribers" DataTable column (right-aligned, sortable, em-dash for null) — identical
  * in the Channels manager and the ChannelDiscovery table, which show subscriber counts on different
@@ -166,6 +166,10 @@ export interface ChannelColumnDeps {
   toggleTag: (channelId: string, tagId: number, hasTag: boolean) => void;
   createAndAttachTag: (channelId: string, name: string) => void;
   onFilterByTag: (tagId: number, name: string) => void;
+  // E8·S4 — suggested user tags per channel (resolved to Tag + confidence), plus accept/dismiss.
+  suggestionsFor: (channelId: string) => SuggestedTag[];
+  onAcceptSuggestion: (channelId: string, tagId: number) => void;
+  onDismissSuggestion: (channelId: string, tagId: number) => void;
 }
 
 export function buildChannelColumns(deps: ChannelColumnDeps): Column<ManagedChannel>[] {
@@ -185,6 +189,9 @@ export function buildChannelColumns(deps: ChannelColumnDeps): Column<ManagedChan
     toggleTag,
     createAndAttachTag,
     onFilterByTag,
+    suggestionsFor,
+    onAcceptSuggestion,
+    onDismissSuggestion,
   } = deps;
   return [
     {
@@ -306,6 +313,9 @@ export function buildChannelColumns(deps: ChannelColumnDeps): Column<ManagedChan
           onToggle={(tagId) => toggleTag(c.id, tagId, c.tag_ids.includes(tagId))}
           onCreate={(name) => createAndAttachTag(c.id, name)}
           onChipClick={onFilterByTag}
+          suggestions={suggestionsFor(c.id)}
+          onAcceptSuggestion={(tagId) => onAcceptSuggestion(c.id, tagId)}
+          onDismissSuggestion={(tagId) => onDismissSuggestion(c.id, tagId)}
         />
       ),
     },