feat(personas): add model config, TUI banner, and fallback system

- Configure per-persona models with temperature/top_p:
  - Zee: cerebras/zai-glm-4.7 (0.8/0.9)
  - Stanley: openrouter/xai/grok-4.1-fast (0.7/0.85)
  - Johny: antigravity/claude-opus-4-5 (0.8/0.9)
- Configure internal agents:
  - title: cerebras/gpt-oss-120b (0.5)
  - compaction: antigravity/gemini-3-flash (0.3)
- Add ASCII art banner on startup with Tab switching
- Sort agents reverse alphabetically (Zee, Stanley, Johny)
- Add provider fallback system with circuit breaker

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.opencode/opencode.jsonc

@@ -13,4 +13,14 @@
     "github-triage": false,
     "github-pr-search": false,
   },
+  "agent": {
+    "title": {
+      "model": "cerebras/gpt-oss-120b",
+      "temperature": 0.5
+    },
+    "compaction": {
+      "model": "antigravity/gemini-3-flash",
+      "temperature": 0.3
+    }
+  },
 }