feat: add runtime provider/model switching via /model <tier> <provider/model>

- ModelRouter: add setClient(), labels map, getLabel(), getAllLabels()
- TUI commands: parse /model <tier> <provider/model> syntax with autocompletion
- TUI minimal: handle provider switching via createClientFromConfig factory
- Daemon: wire initial labels into router config
- Fix /model alias mappings (opus=complex, sonnet=default, haiku=fast)
- Add design doc and update state.json with feature status

src/frontends/tui/minimal.ts

@@ -7,6 +7,7 @@ import { parseCommand, getHelpText, resolveModelAlias, getCommandCompletions, ge
 import { renderMarkdown } from './markdown.js';
 import type { ModelConfig } from '../../config/schema.js';
 import { OllamaClient, LlamaCppClient } from '../../models/index.js';
+import { createClientFromConfig } from '../../daemon/index.js';
 import { loginGitHub } from '../../auth/index.js';
 
 export { parseCommand, type Command };
@@ -180,7 +181,7 @@ export class MinimalTui {
         break;
 
       case 'model':
-        this.handleModelCommand(command.name);
+        this.handleModelCommand(command.name, command.providerModel);
         break;
 
       case 'backend':
@@ -201,21 +202,51 @@ export class MinimalTui {
     }
   }
 
-  private handleModelCommand(name?: string): void {
+  private handleModelCommand(name?: string, providerModel?: string): void {
     const router = this.config.modelRouter;
     if (!router) {
       console.log(`${colors.gray}Model switching not available.${colors.reset}\n`);
       return;
     }
 
-    if (!name) {
-      const current = router.getTier();
-      const available = router.getAvailableTiers();
-      console.log(`${colors.gray}Current model:${colors.reset} ${current}`);
-      console.log(`${colors.gray}Available:${colors.reset} ${available.join(', ')}\n`);
+    // /model <tier> <provider/model> — change a tier's provider and model
+    if (name && providerModel) {
+      const tier = resolveModelAlias(name);
+      const slashIdx = providerModel.indexOf('/');
+      if (slashIdx === -1) {
+        console.log(`${colors.gray}Invalid format. Use provider/model (e.g. anthropic/claude-sonnet-4)${colors.reset}\n`);
+        return;
+      }
+      const provider = providerModel.slice(0, slashIdx);
+      const model = providerModel.slice(slashIdx + 1);
+
+      try {
+        const client = createClientFromConfig({ provider: provider as 'anthropic', model });
+        router.setClient(tier, client, providerModel);
+        console.log(`${colors.gray}Set ${tier} to:${colors.reset} ${providerModel}\n`);
+      } catch (error) {
+        const message = error instanceof Error ? error.message : String(error);
+        console.log(`${colors.gray}Failed to create client:${colors.reset} ${message}\n`);
+      }
       return;
     }
 
+    // /model — show all tiers with labels
+    if (!name) {
+      const current = router.getTier();
+      const available = router.getAvailableTiers();
+      const labels = router.getAllLabels();
+      console.log(`${colors.gray}Active tier:${colors.reset} ${current}`);
+      for (const tier of available) {
+        const label = labels[tier] ?? 'unknown';
+        const marker = tier === current ? ' ←' : '';
+        console.log(`  ${tier}: ${label}${marker}`);
+      }
+      console.log();
+      return;
+    }
+
+    // /model <tier> — switch active tier
     const tier = resolveModelAlias(name);
     if (router.setTier(tier)) {
       // Also update the agent tier so chatWithRouter uses the correct client