Add MiniMax as an Anthropic-compatible AI provider

MiniMax-M3[1m] via api.minimaxi.com/anthropic per the official
Claude Code token-plan docs; the claude-code combo enters the
compatibility matrix as stable with mock regression coverage,
including the Haiku-slot fallback to the single model.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01QKxGW1raAWaqeU8WdHsMsp

cn/registry/ai-compatibility.json

@@ -1,5 +1,5 @@
 {
-  "_verified": "2026-08-24. level=stable: adapter 渲染由 test/shell.d/omarchycn-ai-test.sh mock 回归覆盖; level=official-doc: 官方集成文档存在，native CLI 自管配置",
+  "_verified": "2026-08-25. level=stable: adapter 渲染由 test/shell.d/omarchycn-ai-test.sh mock 回归覆盖; level=official-doc: 官方集成文档存在，native CLI 自管配置",
   "combos": {
     "claude-code": {
       "deepseek": {
@@ -16,6 +16,11 @@
         "level": "stable",
         "doc": "https://docs.z.ai/devpack/tool/claude",
         "adapter": true
+      },
+      "minimax": {
+        "level": "stable",
+        "doc": "https://platform.minimax.io/docs/token-plan/claude-code",
+        "adapter": true
       }
     },
     "codex": {