feat(tui): persist model tier selection and fix formatting

Persist /model tier choice to ~/.local/share/flynn/preferences.json so
it survives restarts. Decode HTML entities (e.g. ') in markdown
renderer output. Suppress noisy logger.info and punycode deprecation
warnings in TUI startup.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/models/router.ts

@@ -14,6 +14,7 @@ export interface ModelRouterConfig {
   tierFallbacks?: Map<ModelTier, ModelClient[]>;
   retryConfig?: RetryConfig;
   labels?: Partial<Record<ModelTier, string>>;
+  onTierChange?: (tier: ModelTier) => void;
 }
 
 export class ModelRouter implements ModelClient {
@@ -25,6 +26,7 @@ export class ModelRouter implements ModelClient {
   private currentTier: ModelTier = 'default';
   private localProviderName?: string;
   private retryConfig?: RetryConfig;
+  private onTierChange?: (tier: ModelTier) => void;
 
   constructor(config: ModelRouterConfig) {
     this.clients = new Map();
@@ -33,6 +35,7 @@ export class ModelRouter implements ModelClient {
     this.fallbackChain = config.fallbackChain;
     this.tierFallbacks = config.tierFallbacks ?? new Map();
     this.retryConfig = config.retryConfig;
+    this.onTierChange = config.onTierChange;
 
     this.clients.set('default', config.default);
     if (config.fast) this.clients.set('fast', config.fast);
@@ -51,11 +54,16 @@ export class ModelRouter implements ModelClient {
   setTier(tier: ModelTier): boolean {
     if (this.clients.has(tier)) {
       this.currentTier = tier;
+      this.onTierChange?.(tier);
       return true;
     }
     return false;
   }
 
+  setOnTierChange(callback: (tier: ModelTier) => void): void {
+    this.onTierChange = callback;
+  }
+
   getTier(): ModelTier {
     return this.currentTier;
   }