fix(tagger): separate JoyTag confidence threshold

Store confidence thresholds per tagger model so JoyTag no longer inherits WD tuning. Refresh the active threshold when switching models, guard stale threshold saves, and keep UI Lab mocks in sync.

Also tightens the onboarding model selector so the segmented control no longer stretches across the row.

src/taggerModels.ts

@@ -1,15 +1,17 @@
 import type { TaggerModel } from "./store";
 
-export const TAGGER_MODELS: Record<TaggerModel, { name: string; tab: string; description: string }> = {
+export const TAGGER_MODELS: Record<TaggerModel, { name: string; tab: string; description: string; defaultThreshold: number }> = {
   wd: {
     name: "WD SwinV2 Tagger v3",
     tab: "WD (anime)",
+    defaultThreshold: 0.35,
     description:
       "Anime-focused vision model by SmilingWolf. Generates booru-style tags with configurable confidence thresholds.",
   },
   joytag: {
     name: "JoyTag",
     tab: "JoyTag (general)",
+    defaultThreshold: 0.4,
     description:
       "Booru-schema tagger that also handles photographic content and is strong on NSFW concepts. The explicitness rating is derived from its tags.",
   },