build: add biome formatter and linter

.opencode/package.json

@@ -12,4 +12,4 @@
     "@types/bun": "^1.3.10",
     "@types/node": "^25.5.0"
   }
-}
+}

.opencode/tools/multi-model.ts

@@ -1,6 +1,7 @@
 // Re-export open and close tools for project-level use via relative paths.
 // For published package usage, change imports to "@username/opencode-multi-model".
-import { openTool } from "../../src/tools/open";
-import { closeTool } from "../../src/tools/close";
 
-export { openTool as open, closeTool as close };
+import { closeTool } from "../../src/tools/close";
+import { openTool } from "../../src/tools/open";
+
+export { closeTool as close, openTool as open };

.opencode/tsconfig.json

@@ -18,9 +18,7 @@
     "noUncheckedIndexedAccess": true,
     "noImplicitOverride": true,
 
-    "types": [
-      "bun-types"
-    ]
+    "types": ["bun-types"]
   },
   "include": ["**/*.ts", "**/*.tsx"]
-}
+}