fix(watchlist): never draw a spot before its verdict

A new spot rendered as Needed the instant it arrived and was withdrawn half a
second later when the worked answer landed — the list twitched on every burst.
Unsettled spots are now invisible everywhere (card lines, counters, the
Active/Needed-only filters) until their verdict is in: nobody needs a spot
150 ms early, they need it settled. The answer map is merged rather than
replaced, so a settled line can never fall back to unknown, and the query
debounce drops to 150 ms since there is nothing on screen waiting for it.

frontend/src/components/WatchlistTab.tsx

@@ -138,16 +138,25 @@ export function WatchlistTab({ spots, spotStatus, onSpotSelect, onSpotClick }: P
       if (queries.length === 0) { setWorked({}); return; }
       try {
         const res: boolean[] = (await WatchlistWorkedSlots(queries as any)) ?? [];
-        const next: Record<string, boolean> = {};
-        keys.forEach((k, i) => { next[k] = !!res[i]; });
-        setWorked(next);
+        // MERGED, not replaced: replacing made every already-answered key
+        // momentarily unknown on each refresh, which re-hid settled lines.
+        setWorked((prev) => {
+          const next = { ...prev };
+          keys.forEach((k, i) => { next[k] = !!res[i]; });
+          return next;
+        });
       } catch { /* the badges just stay conservative */ }
-    }, 400) as unknown as number;
+    }, 150) as unknown as number;
     return () => { if (queryTimer.current) window.clearTimeout(queryTimer.current); };
   }, [spotsFor, entries]);
 
-  const workedFor = (e: WLEntry, s: ClusterSpot): boolean =>
-    worked[`${s.dx_call}|${s.band ?? ''}|${inferSpotMode(s.comment ?? '', s.freq_hz) || ''}|${e.isContest ? 1 : 0}`] ?? false;
+  const wkey = (e: WLEntry, s: ClusterSpot) =>
+    `${s.dx_call}|${s.band ?? ''}|${inferSpotMode(s.comment ?? '', s.freq_hz) || ''}|${e.isContest ? 1 : 0}`;
+  const workedFor = (e: WLEntry, s: ClusterSpot): boolean => worked[wkey(e, s)] ?? false;
+  // A spot whose verdict has not come back yet is NOT drawn. Showing it as
+  // Needed and withdrawing it half a second later made the list twitch on
+  // every burst — and nobody needs a spot 400 ms early, they need it settled.
+  const settled = (e: WLEntry, s: ClusterSpot): boolean => wkey(e, s) in worked;
 
   const add = async () => {
     const c = addCall.trim().toUpperCase();
@@ -173,7 +182,7 @@ export function WatchlistTab({ spots, spotStatus, onSpotSelect, onSpotClick }: P
     if (family === 'normal' && e.isContest) return false;
     if (family === 'contest' && !e.isContest) return false;
     if (search && !e.callsign.includes(search.trim().toUpperCase())) return false;
-    const list = (spotsFor.get(e.callsign) ?? []).filter(modeMatches);
+    const list = (spotsFor.get(e.callsign) ?? []).filter(modeMatches).filter((s2) => settled(e, s2));
     if (activeOnly && list.length === 0) return false;
     if (neededOnly && !list.some((s2) => !workedFor(e, s2))) return false;
     return true;
@@ -182,7 +191,7 @@ export function WatchlistTab({ spots, spotStatus, onSpotSelect, onSpotClick }: P
   const counters = useMemo(() => {
     let active = 0, needed = 0;
     for (const e of entries) {
-      const list = (spotsFor.get(e.callsign) ?? []).filter(modeMatches);
+      const list = (spotsFor.get(e.callsign) ?? []).filter(modeMatches).filter((s2) => settled(e, s2));
       if (list.length > 0) active++;
       if (list.some((s2) => !workedFor(e, s2))) needed++;
     }
@@ -281,7 +290,7 @@ export function WatchlistTab({ spots, spotStatus, onSpotSelect, onSpotClick }: P
             {entries.length === 0 ? t('wl.empty') : t('wl.noneMatch')}
           </div>
         ) : shown.map((e) => {
-          const all = (spotsFor.get(e.callsign) ?? []).filter(modeMatches);
+          const all = (spotsFor.get(e.callsign) ?? []).filter(modeMatches).filter((s2) => settled(e, s2));
           const needed = all.filter((s) => !workedFor(e, s)).length;
           // Needed-only hides the worked LINES as well as the all-worked cards:
           // a filter that says needed and still lists five green Worked rows is